screenshooter: Scale damage by output scale in screen recorder

The damage region is in compositor coords, we need to scale it by
the output scale when using the damage to read output buffer data.

src/screenshooter.c

@@ -330,6 +330,11 @@ transform_rect(struct weston_output *output, pixman_box32_t *r)
         default:
                 break;
         }
+
+	r->x1 *= output->scale;
+	r->y1 *= output->scale;
+	r->x2 *= output->scale;
+	r->y2 *= output->scale;
 }
 
 static void