Fix for collision polygon not working at all on exported builds.

(cherry picked from commit a169e1406de77c3abfe670217f18bcf2c1468bae)

scene/3d/collision_polygon.cpp

@@ -44,7 +44,7 @@ void CollisionPolygon::_build_polygon() {
 	if (polygon.size() == 0)
 		return;
 
-	Vector<Vector<Vector2> > decomp = Geometry::decompose_polygon(polygon);
+	Vector<Vector<Vector2> > decomp = Geometry::decompose_polygon_in_convex(polygon);
 	if (decomp.size() == 0)
 		return;