package/libuio: select gettext when BR2_NEEDS_GETTEXT_IF_LOCALE is set

gettext is added to libuio dependency when BR2_NEEDS_GETTEXT_IF_LOCALE
is set without selecting it at Kconfig level.

Fixes:

  http://autobuild.buildroot.net/results/321688e16596086d1dad6f489d35edbb7fe7a955



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