Add padding if xcb_icccm is not available

include/wlr/xwayland.h

@@ -60,6 +60,8 @@ struct wlr_xwayland_surface {
 	uint32_t motif_hints[5];
 	#ifdef HAS_XCB_ICCCM
 	xcb_size_hints_t size_hints;
+	#else
+	char size_hints_padding[72];
 	#endif
 
 	struct {