I successfully built OpenWrt last week, but now my internal hard drive is full, so I removed the OpenWrt directory and re-cloned and reinstalled on an external USB drive. I'm using Manjaro GNU/Linux. Here's what I ran and the error messages:
[user@system openwrt]$ git status
On branch openwrt-18.06
Your branch is up to date with 'origin/openwrt-18.06'.
nothing to commit, working tree clean
[user@system openwrt]$ ./scripts/feeds update -a
Updating feed 'packages' from 'https://git.openwrt.org/feed/packages.git;openwrt-18.06' ...
Already up to date.
Create index file './feeds/packages.index'
Updating feed 'luci' from 'https://git.openwrt.org/project/luci.git;openwrt-18.06' ...
Already up to date.
Create index file './feeds/luci.index'
Updating feed 'routing' from 'https://git.openwrt.org/feed/routing.git;openwrt-18.06' ...
Already up to date.
Create index file './feeds/routing.index'
Updating feed 'telephony' from 'https://git.openwrt.org/feed/telephony.git;openwrt-18.06' ...
Already up to date.
Create index file './feeds/telephony.index'
[user@system openwrt]$ ./scripts/feeds install -a
WARNING: Makefile 'package/feeds/packages/gnutls/Makefile' has a dependency on 'kmod-cryptodev', which does not exist
Installing all packages from feed packages.
Installing all packages from feed luci.
Installing all packages from feed routing.
Installing all packages from feed telephony.
[user@system openwrt]$ make menuconfig
WARNING: Makefile 'package/feeds/packages/gnutls/Makefile' has a dependency on 'kmod-cryptodev', which does not exist
tmp/.config-package.in:718:warning: ignoring unsupported character '@'
tmp/.config-package.in:718:warning: ignoring unsupported character '@'
tmp/.config-package.in:803:warning: ignoring unsupported character '@'
tmp/.config-package.in:857:warning: ignoring unsupported character '@'
tmp/.config-package.in:857:warning: ignoring unsupported character '@'
tmp/.config-package.in:857:warning: ignoring unsupported character '@'
tmp/.config-package.in:857:warning: ignoring unsupported character '@'
tmp/.config-package.in:857:warning: ignoring unsupported character '@'
tmp/.config-package.in:13380:warning: ignoring unsupported character '@'
tmp/.config-package.in:14349:warning: ignoring unsupported character '@'
tmp/.config-package.in:14762:warning: ignoring unsupported character '@'
tmp/.config-package.in:16283:warning: ignoring unsupported character '@'
tmp/.config-package.in:17420:warning: ignoring unsupported character '@'
tmp/.config-package.in:17420:warning: ignoring unsupported character '@'
tmp/.config-package.in:17434:warning: ignoring unsupported character '@'
tmp/.config-package.in:17434:warning: ignoring unsupported character '@'
tmp/.config-package.in:17448:warning: ignoring unsupported character '@'
tmp/.config-package.in:17448:warning: ignoring unsupported character '@'
tmp/.config-package.in:17461:warning: ignoring unsupported character '@'
tmp/.config-package.in:17461:warning: ignoring unsupported character '@'
tmp/.config-package.in:31997:warning: ignoring unsupported character '@'
tmp/.config-package.in:32001:warning: ignoring unsupported character '@'
tmp/.config-package.in:32038:warning: ignoring unsupported character '@'
tmp/.config-package.in:32045:warning: ignoring unsupported character '@'
tmp/.config-package.in:32075:warning: ignoring unsupported character '@'
tmp/.config-package.in:99770:warning: ignoring unsupported character '@'
tmp/.config-package.in:99770:warning: ignoring unsupported character '@'
tmp/.config-package.in:99770:warning: ignoring unsupported character '@'
tmp/.config-package.in:99770:warning: ignoring unsupported character '@'
tmp/.config-package.in:99770:warning: ignoring unsupported character '@'
tmp/.config-package.in:99770:warning: ignoring unsupported character '@'
tmp/.config-package.in:99773:warning: ignoring unsupported character '@'
tmp/.config-package.in:99773:warning: ignoring unsupported character '@'
tmp/.config-package.in:99788:warning: ignoring unsupported character '@'
tmp/.config-package.in:99788:warning: ignoring unsupported character '@'
tmp/.config-package.in:99788:warning: ignoring unsupported character '@'
tmp/.config-package.in:99788:warning: ignoring unsupported character '@'
tmp/.config-package.in:99788:warning: ignoring unsupported character '@'
tmp/.config-package.in:99788:warning: ignoring unsupported character '@'
tmp/.config-package.in:99811:warning: ignoring unsupported character '@'
tmp/.config-package.in:99811:warning: ignoring unsupported character '@'
tmp/.config-package.in:99811:warning: ignoring unsupported character '@'
tmp/.config-package.in:99811:warning: ignoring unsupported character '@'
tmp/.config-package.in:99811:warning: ignoring unsupported character '@'
tmp/.config-package.in:99811:warning: ignoring unsupported character '@'
configuration written to .config
*** End of the configuration.
*** Execute 'make' to start the build or try 'make help'.
[user@system openwrt]$ make -j1 V=s
WARNING: Makefile 'package/feeds/packages/gnutls/Makefile' has a dependency on 'kmod-cryptodev', which does not exist
time: target/linux/prereq#0.18#0.10#0.37
make[1]: Entering directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt'
make[2]: Entering directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt'
+ mkdir -p /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/target-mips_24kc_musl
+ cd /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/target-mips_24kc_musl
+ mkdir -p bin lib include stamp
mkdir -p /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/build_dir/target-mips_24kc_musl/stamp
touch /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/target-mips_24kc_musl/.prepared
+ mkdir -p /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host
+ cd /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host
+ mkdir -p bin lib include stamp
mkdir -p /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/build_dir/host/stamp /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host/include/sys
install -m0644 /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/tools/include/*.h /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host/include/
install -m0644 /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/tools/include/sys/*.h /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host/include/sys/
ln -sf lib /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host/lib64
touch /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host/.prepared
make[3]: Entering directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/tools/flock'
make[3]: Leaving directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/tools/flock'
time: tools/flock/compile#0.08#0.04#0.17
make[3]: Entering directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/tools/sed'
make -C /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/build_dir/host/sed-4.5 SHELL="bash"
make[4]: Entering directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/build_dir/host/sed-4.5'
cd . && bash /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/build_dir/host/sed-4.5/build-aux/missing automake-1.16 --gnu Makefile
autom4te: need GNU m4 1.4 or later: /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/host/bin/m4
automake-1.16: error: autoconf failed with exit status: 1
make[4]: *** [Makefile:2088: Makefile.in] Error 1
make[4]: Leaving directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/build_dir/host/sed-4.5'
make[3]: *** [Makefile:46: /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/build_dir/host/sed-4.5/.built] Error 2
make[3]: Leaving directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/tools/sed'
time: tools/sed/compile#0.45#0.30#0.82
make[2]: *** [tools/Makefile:154: tools/sed/compile] Error 2
make[2]: Leaving directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt'
make[1]: *** [tools/Makefile:150: /run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/staging_dir/target-mips_24kc_musl/stamp/.tools_compile_yynyyyyynyyyyynyynyyyyyyyyyyyyyyyyyyyyynyynynyyyynnyy] Error 2
make[1]: Leaving directory '/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt'
make: *** [/run/media/user/USBdrive/GitDev/GitHub-OpenWrt/openwrt/include/toplevel.mk:218: world] Error 2
[user@system openwrt]$