libc/glibc: add option to force unwind

We make it an option, as not all combinations of architectures
vs. compiler vs. glibc/eglibc exhibit the issue. Mostly visible
on old glibc versions, it seems...

This is a missing part from the glibc/eglibc merger... :-/

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

 #!/bin/sh

 # Needed for systems without gettext

 $* -xc -o /dev/null - > /dev/null 2>&1 << EOF

 #include <libintl.h>

 int main()

 {

 	gettext("");

 	return 0;

 }

 EOF

 if [ ! "$?" -eq "0"  ]; then

 	echo -DKBUILD_NO_NLS;

 fi