See card: https://favro.com/organization/c564ede4ed3337f7b17986b6/c49f564b3ca1630d4475d838?card=Uni-56056 for clarity

Steps to repro:

1. Download the project: https://drive.google.com/open?id=1Iue9L3TKB4b92ZE1uaRM0ZoFWusUkDFE
2. Open the project and ‘LabsShadowmask’ scene;
3. Go to Edit>Preferences>GI Cache;
4. Set Minimum Cache Size to 5;
5. Bake the scene with CPU LM.

Expected result:
Baking finishes successfully.

Actual result:
Baking stalls with the following errors:

(Filename: C:\UnityTrunkRepo\trunk\xxx\Editor/Src/GI/Jobs/WriteLightingDataAssetJob.cpp Line: 62)
Failed to copy lightmap snapshot assets to directory: Temp/GI/6f0b40ff420559782353ab4d7dfa58f1
(Filename: C:\UnityTrunkRepo\trunk\xxx\Editor/Src/GI/Jobs/WriteLightingDataAssetJob.cpp Line: 283)

Notes:
- Reproducible in 2018.3.0a10;
- Reproducible on Windows 10
- Reproduces with bigger Minimum Cache size (10GB, 15GB).
- Reproduced when baking either with CPU or GPU Lightmapper.