SceneCaptureCube::PostActorCreated() fails compile

SceneCaptureCube::PostActorCreated() is not set with "ENGINE_API" and causes compile errors when trying to use a class that inherits from SceneCaptureCube.

1. Open SceneCaptureCube.h
2. Go to line 31 "virtual void PostActorCreated() override;"

Result:
Without Engine_API, attempting to call this function causes compile errors