ecryptfs-utils: select gettext, needed for command line utilities

The ecryptfs-utils package requires the 'gettext' program, which is
provided by the gettext package, to get translated strings. This is
needed regardless of whether the toolchain uses glibc or uClibc.

This issue was reported by 'ausjke' on IRC.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>