This will be set in servo/saltfs to prevent our buildbot builders from re-downloading the build tools for every build.
r? @larsbergstrom or @metajack or @Manishearth
This eliminates the
Synchronizing submodule url for 'support/android-rs-glue'
Synchronizing submodule url for 'tests/wpt/web-platform-tests'
messages that appeared for every `mach build` command.
This avoids changing any directories outside the repo, which is better for
some automation scenarios.
The servobuild.example file has a "cache-dir" setting that restores the
previous default location of `~/.servo`, which is useful for developers
working with multiple clones on the same machine.
That way, whenever rust-snapshot-hash changes, mach will look for
the Rust snapshot in a different directory and re-boostrap as needed.
However, older rust version will be left behind never cleaned up.
This is good for git-bisect, but not for disk space:
the current snapshot is 618 MB.
In the future, we may want `mach clean` or some other comment
to remove unused Rust snapshots.
CC #3388
