tools: gnulib: remove stale gl_-prefixed macros from staging

Commit c820f097e0 ("tools: gnulib: install .m4 file with gl_ prefix")
installed gnulib autoconf macros under gl_-prefixed file names. The
scheme was later reverted in commit cda598a595, but the previously
installed files were never removed from share/aclocal.

As aclocal reads the whole directory, stale gl_*.m4 files can override
the current unprefixed macros. This breaks elfutils builds on macOS
after the gnulib stable-202507 update, resulting in empty #if
expressions in the generated ctype.h.

Remove the stale files in Host/Uninstall. Host/Install calls it first,
so affected build trees are cleaned up automatically on the next
gnulib reinstall.

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/24759
Signed-off-by: Robert Marko <robimarko@gmail.com>

tools/gnulib/Makefile

@@ -23,6 +23,7 @@ endef
 
 define Host/Uninstall
 	rm -rf $(STAGING_DIR_HOST)/bin/gnulib-tool $(STAGING_DIR_HOST)/share/gnulib
+	rm -f $(STAGING_DIR_HOST)/share/aclocal/gl_*.m4
 endef
 
 $(eval $(call HostBuild))