libc/glibc: use the common start_files procedure

Use the common procedure, shared between glibc and eglibc. This requires
that glibc-specific bits be included in the shared procedure.

But still build the full libc with the glibc-specific procedure. This will
be commonalised in a future commit.

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