When Building Light for a SubLevel of a project, BSPs will be built into the level regardless if hidden or not

BSPs will be built with light/shadow extrapolated even if they are placed in a hidden sub_level of the project at the time of building.

Also Tested in 4.10.4, 4.11 Preview 6 and Dev-Editor-CL-2877235

*Quick Repro - Open the Attached 4.12 Project and Build Lighting for SubLevel_01 only*

1. Create a Blank Project with NO Starter Content
2. Save the default Unititled Level as Persistent.umap
3. Open the Level Browser
4. Create a New Level called Sub_Level_01
5. Create a New Level called Sub_Level_02
6. Select all items in the Persistent Level except the Player Start and move to the Sub_Level_01
7. With Sub_Level_02 set to the working level, add a BSP object into the map
8. Back in the Level Browser, hide Sub_Level_02 (This should only hide the BSP.)
9. Set the Directional Light to Static
10. Build Lighting

RESULTS: The BSP will pop back up and light will be built around it in Sub_Level_01 even though it is hidden via Sub_Level _02

EXPECTED: The BSP should not be built nor should lighting be built around it.