How to reproduce:
1. Open the attached project "1268383.zip"
2. Open the "SampleScene" Scene
3. Click "Tools" > "Populate" and wait till script finishes (this may take 20-30 minutes)
4. Check the memory usage of the Editor using the Task Manager (or equivalent program). If it is between 400 and 800MB proceed to the next step, otherwise restart the Editor before proceeding
5. Build and run the Player with a "SampleScene" Scene
6. Observe the memory usage in the Task Manager

Expected result: memory usage stays between 600MB and 1GB through the entire build process
Actual result: memory usage rises to about 10GB while building the project

Reproducible with: 2020.1.0b9, 2020.2.0a9
Not reproducible with: 2018.4.26f1, 2019.4.6f1, 2020.1.0b8, 2020.2.0a8

Notes:
- Make sure to delete the project Library folder each time before trying to reproduce the issue
- Only reproduces when the Scene in a build references 200-300 assets
- The more assets are assigned to the "References" GameObject Scene References Component's References array the more memory is used when building
- Make sure to disable Unity Accelerator before trying to reproduce