Reproduction steps:
1. Open project attached(case_904483-unity_progressive_lightmapper_test.zip).
2. Open scene "Shadowmask"
3. Build for standalone player.

Expected result: It will succeed.
Actual result: After it succeeds, memory leak appears and due to that, Unity crashes.

Note: Some errors used to appear like "Clustering failed due to lack of memory" and it needed like 32gb of it. They disappeared after few restarts.

Reproduced on: 2017.1.0b2
Worked fine on: 2017.1.0b1