package/m4: fix build with glibc 2.34

package/m4: fix build with glibc 2.34

m4 fails to build with glibc 2.34 because SIGSTKSZ is now a run-time
variable since
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=6c57d320484988e87e446e2e60ce42816bf51d53

So backport an upstream patch from gnulib, see:
https://lists.gnu.org/archive/html/bug-m4/2021-03/msg00015.html

An other option would have been to apply patch from
https://lists.gnu.org/archive/html/bug-m4/2021-03/msg00024.html
but no feedback was received on this patch

Fixes:
 - https://bugs.buildroot.org/show_bug.cgi?id=13721

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>