Zlib is autorebuilt each time on sdk 19.07.5+

I'm using the SDK (on docker) and found a problem with autorebuilds. Since 19.07.5 including 21.02.0 the zlib package is rebuilt each time i run make package/zlib/compile, which also triggers a rebuild of packages that depend on zlib, for example ncurses.

A work-around is to patch include/package.mk as shown below, which reverts a change from commit 605adb10 "download: handle possibly invalid local tarballs":

$ diff -u include/package.mk{.orig,}
--- include/package.mk.orig     2021-09-07 18:31:27.463442970 +0000
+++ include/package.mk  2021-09-07 19:26:08.390457191 +0000
@@ -185,7 +185,7 @@
   $(call Build/Autoclean)
   $(call DefaultTargets)
+#  $(DL_DIR)/$(FILE): FORCE
        $(foreach hook,$(Hooks/Download),