enable building the game engine without bullet for scons & cmake

source/gameengine/Ketsji/KX_GameObject.cpp

@@ -1574,11 +1574,11 @@ PyObject* KX_GameObject::PyReinstancePhysicsMesh(PyObject* args)
 		) {
 		return NULL;
 	}
-	
+#ifdef USE_BULLET
 	/* gameobj and mesh can be NULL */
 	if(KX_ReInstanceBulletShapeFromMesh(this, gameobj, mesh))
 		Py_RETURN_TRUE;
-
+#endif
 	Py_RETURN_FALSE;
 }