gettext: disable nls when INHIBIT_DEFAULT_DEPS is set

gettext: disable nls when INHIBIT_DEFAULT_DEPS is set

* for example in gcc-runtime DEPENDS_GETTEXT from gettext.bbclass isn't
  used because gcc-runtime recipes also set INHIBIT_DEFAULT_DEPS,
  explicitly disable NLS when DEPENDS_GETTEXT is empty
* this is causing undeterministic build
  if you compare i586-oe-linux/libstdc++-v3/config.log in WORKDIR when building
  gcc-runtime before and after building gettext-native you'll see that msgfmt
  isn't found in one of them and gcc-runtime-locale-{de,fr} packages
  aren't created, there is only one file in them:
  gcc-runtime-locale-de/usr/share/locale/de/LC_MESSAGES/libstdc++.mo

(From OE-Core rev: 8f0b07fc53c94426efa3557424328b52a61e7305)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>