patches/openwrt: Backport m4 update
Fix build with new enough system, otherwise build ends with the following error:
ccache gcc -I. -I/home/fast/miska/omnia-build/staging_dir/host/include -O2 -I/home/fast/miska/omnia-build/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
In file included from /usr/include/signal.h:328,
from ./signal.h:52,
from c-stack.c:49:
c-stack.c:55:26: error: missing binary operator before token "("
55 | #elif HAVE_LIBSIGSEGV && SIGSTKSZ < 16384
| ^~~~~~~~
c-stack.c:134:8: error: variably modified 'buffer' at file scope
134 | char buffer[SIGSTKSZ];
| ^~~~~~
make[6]: *** [Makefile:1910: c-stack.o] Error 1