Trying to get MPTCP, I followed a link on the official docs to this GitHub repo. It seems to be a decade old but maybe that's just the creation date, so without much else to choose from, I went from there. It seems to have very current stuff that I know it's maybe a couple of years old max once you run it though.
I'm not a developer, perhaps I should've started with that. But more or less I get around. In the past I successfully compiled HAProxy, for what it's worth, but that's about it.
I followed the guides to the letter. I got the pre-made and slightly older Debian 11 VM recommended in the guide vs just cloning one of my goldenmasters. I found errors every step of the way, but in the end I've been able to get rid of them or minimize them to that kind that's just informational and you're allowed to move to the next step. I hope that makes sense.
When it starts to build, or compile, or something; it passes all the checks without having to force it and starts working, it seems, but it fails when it gets to m4 every time.
{make V=s} output
[Thu08@15:38:55][root@wrtbuilder:~/openwrt] #〉make V=s
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/clean'
<-- More of the same. Cut out to reduce already-reached character count -->
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/distcheck'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/configure'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/configure'
make[1]: Entering directory '/root/openwrt'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/clean'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/clean'
<-- More of the same. Cut out to reduce already-reached character count -->
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/configure'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/configure'
make[2]: Entering directory '/root/openwrt'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/clean'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/clean'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/download'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/download'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/prepare'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/prepare'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/compile'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/compile'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/install'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/install'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/update'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/update'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/refresh'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/refresh'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/prereq'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/prereq'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/dist'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/dist'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/distcheck'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/distcheck'
package/Makefile:174: warning: overriding recipe for target 'package/openvpn/configure'
package/Makefile:174: warning: ignoring old recipe for target 'package/openvpn/configure'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/clean'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/clean'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/download'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/download'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/prepare'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/prepare'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/compile'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/compile'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/install'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/install'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/update'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/update'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/refresh'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/refresh'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/prereq'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/prereq'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/dist'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/dist'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/distcheck'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/distcheck'
package/Makefile:174: warning: overriding recipe for target 'package/xtables-addons/configure'
package/Makefile:174: warning: ignoring old recipe for target 'package/xtables-addons/configure'
+ mkdir -p /root/openwrt/staging_dir/target-x86_64_uClibc-0.9.33.2
+ cd /root/openwrt/staging_dir/target-x86_64_uClibc-0.9.33.2
+ mkdir -p bin lib include stamp
mkdir -p /root/openwrt/build_dir/target-x86_64_uClibc-0.9.33.2/stamp
touch /root/openwrt/staging_dir/target-x86_64_uClibc-0.9.33.2/.prepared
+ mkdir -p /root/openwrt/staging_dir/host
+ cd /root/openwrt/staging_dir/host
+ mkdir -p bin lib include stamp
mkdir -p /root/openwrt/build_dir/host/stamp /root/openwrt/staging_dir/host/include/sys
install -m0644 /root/openwrt/tools/include/*.h /root/openwrt/staging_dir/host/include/
install -m0644 /root/openwrt/tools/include/sys/*.h /root/openwrt/staging_dir/host/include/sys/
ln -sf lib /root/openwrt/staging_dir/host/lib64
touch /root/openwrt/staging_dir/host/.prepared
make[3]: Entering directory '/root/openwrt/tools/patch'
make[3]: Leaving directory '/root/openwrt/tools/patch'
make[3]: Entering directory '/root/openwrt/tools/patch'
make[3]: Leaving directory '/root/openwrt/tools/patch'
make[3]: Entering directory '/root/openwrt/tools/m4'
make -C /root/openwrt/build_dir/host/m4-1.4.17
make[4]: Entering directory '/root/openwrt/build_dir/host/m4-1.4.17'
make all-recursive
make[5]: Entering directory '/root/openwrt/build_dir/host/m4-1.4.17'
Making all in .
make[6]: Entering directory '/root/openwrt/build_dir/host/m4-1.4.17'
make[6]: Nothing to be done for 'all-am'.
make[6]: Leaving directory '/root/openwrt/build_dir/host/m4-1.4.17'
Making all in examples
make[6]: Entering directory '/root/openwrt/build_dir/host/m4-1.4.17/examples'
make[6]: Nothing to be done for 'all'.
make[6]: Leaving directory '/root/openwrt/build_dir/host/m4-1.4.17/examples'
Making all in lib
make[6]: Entering directory '/root/openwrt/build_dir/host/m4-1.4.17/lib'
make all-am
make[7]: Entering directory '/root/openwrt/build_dir/host/m4-1.4.17/lib'
depbase=`echo gl_avltree_oset.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT gl_avltree_oset.o -MD -MP -MF $depbase.Tpo -c -o gl_avltree_oset.o gl_avltree_oset.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo binary-io.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT binary-io.o -MD -MP -MF $depbase.Tpo -c -o binary-io.o binary-io.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo c-stack.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT c-stack.o -MD -MP -MF $depbase.Tpo -c -o c-stack.o c-stack.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo clean-temp.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT clean-temp.o -MD -MP -MF $depbase.Tpo -c -o clean-temp.o clean-temp.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo cloexec.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT cloexec.o -MD -MP -MF $depbase.Tpo -c -o cloexec.o cloexec.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo close-stream.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT close-stream.o -MD -MP -MF $depbase.Tpo -c -o close-stream.o close-stream.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo closein.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT closein.o -MD -MP -MF $depbase.Tpo -c -o closein.o closein.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo closeout.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT closeout.o -MD -MP -MF $depbase.Tpo -c -o closeout.o closeout.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo dirname.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT dirname.o -MD -MP -MF $depbase.Tpo -c -o dirname.o dirname.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo dirname-lgpl.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT dirname-lgpl.o -MD -MP -MF $depbase.Tpo -c -o dirname-lgpl.o dirname-lgpl.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo execute.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT execute.o -MD -MP -MF $depbase.Tpo -c -o execute.o execute.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo exitfail.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT exitfail.o -MD -MP -MF $depbase.Tpo -c -o exitfail.o exitfail.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fatal-signal.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fatal-signal.o -MD -MP -MF $depbase.Tpo -c -o fatal-signal.o fatal-signal.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fd-hook.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fd-hook.o -MD -MP -MF $depbase.Tpo -c -o fd-hook.o fd-hook.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fd-safer-flag.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fd-safer-flag.o -MD -MP -MF $depbase.Tpo -c -o fd-safer-flag.o fd-safer-flag.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo dup-safer-flag.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT dup-safer-flag.o -MD -MP -MF $depbase.Tpo -c -o dup-safer-flag.o dup-safer-flag.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo filenamecat.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT filenamecat.o -MD -MP -MF $depbase.Tpo -c -o filenamecat.o filenamecat.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo filenamecat-lgpl.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT filenamecat-lgpl.o -MD -MP -MF $depbase.Tpo -c -o filenamecat-lgpl.o filenamecat-lgpl.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fopen-safer.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fopen-safer.o -MD -MP -MF $depbase.Tpo -c -o fopen-safer.o fopen-safer.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo freading.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT freading.o -MD -MP -MF $depbase.Tpo -c -o freading.o freading.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo gl_linkedhash_list.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT gl_linkedhash_list.o -MD -MP -MF $depbase.Tpo -c -o gl_linkedhash_list.o gl_linkedhash_list.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo localcharset.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT localcharset.o -MD -MP -MF $depbase.Tpo -c -o localcharset.o localcharset.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo glthread/lock.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT glthread/lock.o -MD -MP -MF $depbase.Tpo -c -o glthread/lock.o glthread/lock.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo malloca.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT malloca.o -MD -MP -MF $depbase.Tpo -c -o malloca.o malloca.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo pipe2.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT pipe2.o -MD -MP -MF $depbase.Tpo -c -o pipe2.o pipe2.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo pipe2-safer.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT pipe2-safer.o -MD -MP -MF $depbase.Tpo -c -o pipe2-safer.o pipe2-safer.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo progname.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT progname.o -MD -MP -MF $depbase.Tpo -c -o progname.o progname.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo quotearg.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT quotearg.o -MD -MP -MF $depbase.Tpo -c -o quotearg.o quotearg.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo sig-handler.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT sig-handler.o -MD -MP -MF $depbase.Tpo -c -o sig-handler.o sig-handler.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo spawn-pipe.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT spawn-pipe.o -MD -MP -MF $depbase.Tpo -c -o spawn-pipe.o spawn-pipe.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo mkstemp-safer.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT mkstemp-safer.o -MD -MP -MF $depbase.Tpo -c -o mkstemp-safer.o mkstemp-safer.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo tempname.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT tempname.o -MD -MP -MF $depbase.Tpo -c -o tempname.o tempname.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo glthread/tls.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT glthread/tls.o -MD -MP -MF $depbase.Tpo -c -o glthread/tls.o glthread/tls.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo tmpdir.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT tmpdir.o -MD -MP -MF $depbase.Tpo -c -o tmpdir.o tmpdir.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo unistd.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT unistd.o -MD -MP -MF $depbase.Tpo -c -o unistd.o unistd.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo dup-safer.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT dup-safer.o -MD -MP -MF $depbase.Tpo -c -o dup-safer.o dup-safer.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fd-safer.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fd-safer.o -MD -MP -MF $depbase.Tpo -c -o fd-safer.o fd-safer.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo pipe-safer.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT pipe-safer.o -MD -MP -MF $depbase.Tpo -c -o pipe-safer.o pipe-safer.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo verror.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT verror.o -MD -MP -MF $depbase.Tpo -c -o verror.o verror.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo version-etc.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT version-etc.o -MD -MP -MF $depbase.Tpo -c -o version-etc.o version-etc.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo version-etc-fsf.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT version-etc-fsf.o -MD -MP -MF $depbase.Tpo -c -o version-etc-fsf.o version-etc-fsf.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo wait-process.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT wait-process.o -MD -MP -MF $depbase.Tpo -c -o wait-process.o wait-process.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo wctype-h.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT wctype-h.o -MD -MP -MF $depbase.Tpo -c -o wctype-h.o wctype-h.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo xmalloc.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT xmalloc.o -MD -MP -MF $depbase.Tpo -c -o xmalloc.o xmalloc.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo xalloc-die.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT xalloc-die.o -MD -MP -MF $depbase.Tpo -c -o xalloc-die.o xalloc-die.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo xmalloca.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT xmalloca.o -MD -MP -MF $depbase.Tpo -c -o xmalloca.o xmalloca.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo xprintf.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT xprintf.o -MD -MP -MF $depbase.Tpo -c -o xprintf.o xprintf.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo xvasprintf.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT xvasprintf.o -MD -MP -MF $depbase.Tpo -c -o xvasprintf.o xvasprintf.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo asprintf.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT asprintf.o -MD -MP -MF $depbase.Tpo -c -o asprintf.o asprintf.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fclose.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fclose.o -MD -MP -MF $depbase.Tpo -c -o fclose.o fclose.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fcntl.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fcntl.o -MD -MP -MF $depbase.Tpo -c -o fcntl.o fcntl.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fflush.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fflush.o -MD -MP -MF $depbase.Tpo -c -o fflush.o fflush.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo fpurge.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT fpurge.o -MD -MP -MF $depbase.Tpo -c -o fpurge.o fpurge.c &&\
mv -f $depbase.Tpo $depbase.Po
depbase=`echo freadahead.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -I. -I/root/openwrt/staging_dir/host/include -O2 -I/root/openwrt/staging_dir/host/include -MT freadahead.o -MD -MP -MF $depbase.Tpo -c -o freadahead.o freadahead.c &&\
mv -f $depbase.Tpo $depbase.Po
freadahead.c: In function 'freadahead':
freadahead.c:91:3: error: #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."
91 | #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."
| ^~~~~
make[7]: *** [Makefile:1837: freadahead.o] Error 1
make[7]: Leaving directory '/root/openwrt/build_dir/host/m4-1.4.17/lib'
make[6]: *** [Makefile:1602: all] Error 2
make[6]: Leaving directory '/root/openwrt/build_dir/host/m4-1.4.17/lib'
make[5]: *** [Makefile:1506: all-recursive] Error 1
make[5]: Leaving directory '/root/openwrt/build_dir/host/m4-1.4.17'
make[4]: *** [Makefile:1461: all] Error 2
make[4]: Leaving directory '/root/openwrt/build_dir/host/m4-1.4.17'
make[3]: *** [Makefile:31: /root/openwrt/build_dir/host/m4-1.4.17/.built] Error 2
make[3]: Leaving directory '/root/openwrt/tools/m4'
make[2]: *** [tools/Makefile:161: tools/m4/compile] Error 2
make[2]: Leaving directory '/root/openwrt'
make[1]: *** [tools/Makefile:159: /root/openwrt/staging_dir/target-x86_64_uClibc-0.9.33.2/stamp/.tools_install_yynyynynynyyyyyyyyyynyyyyyyyynyyyynnyyynnyynnnyyyy] Error 2
make[1]: Leaving directory '/root/openwrt'
make: *** [/root/openwrt/include/toplevel.mk:173: world] Error 2
[Thu08@15:39:15][root@wrtbuilder:~/openwrt] #〉
m4 is installed. It shows in apt search. One thing I thought was notable though, came up while checking for which command confirming being installed had the least output. Piping it through regex (apt list --installed | rgrep -i '^m4.*') definitely wasn't but instead I think it broke apt. What was notable, for me at least, is that that one odd line that was wrapped from being too long, just happened to mention freadahead, as if taunting me. 
I don't think it's related though. Just it laughing at my face.
Could you tell me what the issue is? How to fix it?
Or alternatively,
OpenWRT has this distro-building web app (pictured below); can it be used to create an OpenWRT image with multipath TCP support? I found this awesome Xgrid-like distributed compiler thing, I think (?), but I'm pretty sure it won't cover MPTCP. Assuming I can set it up in the first place.
The web app. It only, as I gather, bundles packages, but from what I understand, MPTCP, like drivers, are things that compile right into the kernel. Correct?. On the other hand though, MPTCP is supposed to be built-in in the Linux kernel since computers ran on burning wood. It's definitely on at least the two youngest versions of Debian and RHEL, make that at least 5 for Fedora, and I've remember reading right here something that OpenWRT had switched MPTCP versions, 1 to 1.1 or something like that. It was on reference to the latter not being backwards-compatible, I believe, but the point is that it seemingly implied it's there already. On the masters I have, x86-64 v23.05 VMs, one on EFI, on one BIOS, it's not. It's kind of confusing.
Could it be used to build an image with MPTCP? I used it to build an image with USB support already… which are drivers, which <see above>.
It was for this old router I found to play with so I could put the /on an SD card (it worked). Can it??
Thanks!