libc/glibc: always enable obsolete RPC

Since unrecognised ./configure flags are simply ignored,
we can always pass --enable-obsolete-rpc.

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

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

 printf "Done. You may now run:\n    ./configure\n"