intl: Revert "Add special hack for GCC" from 2022-06-21.

intl: Revert "Add special hack for GCC" from 2022-06-21.

The added option --enable-host-shared has the same effect as the
libtool-provided option --with-pic, and gcc's Makefile.def actually
uses --with-pic, not --enable-host-shared.

* gettext-runtime/intl/configure.ac: Don't accept option --enable-host-shared.
Don't set PICFLAG.
* gettext-runtime/intl/Makefile.am (AM_CFLAGS): Remove the PICFLAG.
* gnulib-local/modules/gettext-runtime-intl-misc (Makefile.am): Remove the
PICFLAG from AM_CFLAGS.