installer_cross: Enable nls when possible
With crosser-2.0 it's possible to have nls in installer_cross builds. Qt-client fails to build with nls enabled with crosser, so do not enable nls when Qt-client is being built. Otherwise enable it.
With crosser-2.0 it's possible to have nls in installer_cross builds. Qt-client fails to build with nls enabled with crosser, so do not enable nls when Qt-client is being built. Otherwise enable it.