Workaround gears depending on cairo-gl

Extremely hacky, but at least it doesn't stop the build anymore.

clients/gears.c

@@ -222,10 +222,13 @@ allocate_buffer(struct gears *gears)
 	window_draw(gears->window);
 
 	gears->surface[gears->current] = window_get_surface(gears->window);
-
+#ifdef HAVE_CAIRO_GL
 	image = display_get_image_for_drm_surface(gears->display,
 						  gears->surface[gears->current]);
-
+#else /* XXX: hack to make Wayland compile, even if this example doesn't run */
+	die("gears cannot allocate buffer: it was compiled without cairo-gl");
+	return;
+#endif
 	if (!eglMakeCurrent(gears->display, NULL, NULL, gears->context))
 		die("faile to make context current\n");
 

clients/window.h

@@ -51,10 +51,12 @@ display_get_compositor(struct display *display);
 EGLDisplay
 display_get_egl_display(struct display *d);
 
+#ifdef HAVE_CAIRO_GL
 EGLImageKHR
 display_get_image_for_drm_surface(struct display *display,
 				  cairo_surface_t *surface);
 #endif
+#endif
 
 cairo_surface_t *
 display_create_surface(struct display *display,