compositor-x11: Hide update_xkb_keymap behind #ifdef HAVE_XCB_XKB

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
diff --git a/src/compositor-x11.c b/src/compositor-x11.c
index ee3df31..73e71ed 100644
--- a/src/compositor-x11.c
+++ b/src/compositor-x11.c
@@ -290,6 +290,7 @@
 #endif
 }
 
+#ifdef HAVE_XCB_XKB
 static void
 update_xkb_keymap(struct x11_compositor *c)
 {
@@ -303,6 +304,7 @@
 	weston_seat_update_keymap(&c->core_seat, keymap);
 	xkb_keymap_unref(keymap);
 }
+#endif
 
 static int
 x11_input_create(struct x11_compositor *c, int no_input)