[jingwen]

Output directories are unique by the user and source project workspace directory. Output artifacts don't clobber, even though they are all in ~/.cache.

[e40]

Other reasons to avoid the home directory:

1. It might be NFS mounted.

2. Space might be an issue and more difficult to plan for if build outputs are going there.

[jingwen]

The location is not hard-coded and can be configured with the --output_base flag.