intl: Add special hack for GCC.
Based on the commit
https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=4a1493f0603262a7dc1114d9827353e9810e63dc
by Jakub Jelinek <jakub@redhat.com>.
* gettext-runtime/intl/configure.ac: Accept option --enable-host-shared.
Set PICFLAG.
* gettext-runtime/intl/Makefile.am (AM_CFLAGS): Add the PICFLAG.
* gnulib-local/modules/gettext-runtime-intl-misc (Makefile.am): Add the PICFLAG
to AM_CFLAGS.
