package/ltris: fix linking with intl

ltris doen't build with (e)glibc toolchain since commit 454a4101
when gettext package is selected.

With (e)glibc libintl is provided by the libc whereas with uClibc it's provided by gettext.

Linking with intl is only needed if the toolchain needs gettext and locale is set.

Fixes:
http://autobuild.buildroot.net/results/821/82128cb9f5cd6ae2595a8302462f1b5719dad9f7/build-end.log



Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>