AssetBundleGraph: Update PrefabBuilder script does not update prefab

[hiroki-o]

Original report by CS (Bitbucket: optimisez, GitHub: optimisez).

---

When you update the PrefabBuilder script, for example, add box collider component it will not update the prefab with box collider component attached after pressing build button for second times. The current workaround is to change the SerializeField variable from Create Prefab From Group node each time to notify AssetBundleGraph that the prefab needs to update. Seems like there are no mechanics currently to detect the new changes of updated PrefabBuilder script.

[hiroki-o]

Original comment by Hiroki Omae (Bitbucket: [Hiroki Omae](https://bitbucket.org/Hiroki Omae), ).

---

The Version variable in CustomPrefabBuilder is prepared for this purpose. When you update PrefabBuilder script that requires all prefabs updated, you can do so by modifying CustomPrefabBuilder.

I.e. you can set your script version like this. Modifying version string will always trigger prefab rebuild.

[CustomPrefabBuilder("MyPrefabBuilder")]

[CustomPrefabBuilder("MyPrefabBuilder", "ver.2")]