build-sys: set glib dependency version

Further meson configuration tests are to be added based on the glib
version. Also correct the version reporting in the config log.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>