debug/gdb: always enable expat for the cross-gdb

There's no point in not supporting XML in the cross-gdb.
I mean, come on... ;-)

It's still the responsibility of the user to have the necessary
devel expat packages installed for his/her distro.

Reported-by: Trevor Woerner <twoerner@gmail.com>
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"