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>

 This is NOT the official version of dialog.  This version has been

 significantly modified from the original.  It is for use by the Linux

 kernel configuration script.  Please do not bother Savio Lam with 

 questions about this program.