package/procps-ng: fix linking with intl

procps-ng doesn't build with (e)glibc toolchain 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/3e8/3e8464e0b00ce22fa02a6337159fca250d86425c/build-end.log



Signed-off-by: Romain Naour <romain.naour@openwide.fr>
Tested-by: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>