tools/coreutils: fix compilation on macOS 14

tools/coreutils: fix compilation on macOS 14

Current coreutils 8.32 in 22.03 will fail to compile when using macOS 14 with:
depbase=`echo lib/obstack.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc  -I. -I./lib  -Ilib -I./lib -Isrc -I./src -I/Volumes/OpenWrt/openwrt/staging_dir/host/include    -O2 -I/Volumes/OpenWrt/openwrt/staging_dir/host/include  -MT lib/obstack.o -MD -MP -MF $depbase.Tpo -c -o lib/obstack.o lib/obstack.c &&\
mv -f $depbase.Tpo $depbase.Po
lib/obstack.c:351:31: error: incompatible function pointer types initializing 'void (*)(void) __attribute__((noreturn))' with an expression of type 'void (void)' [-Wincompatible-function-pointer-types]
__attribute_noreturn__ void (*obstack_alloc_failed_handler) (void)
                              ^
1 error generated.

Backporting gnulib commit ("obstack: Fix a clang warning") fixes this.

Fixes: #15270
Signed-off-by: Robert Marko <robimarko@gmail.com>