I'm punting on a few things for the first cut at Rust support: - [x] [Handle rustup overrides](https://github.com/mozilla/sccache/issues/87) - [x] [Support linking against native libraries](https://github.com/mozilla/sccache/issues/88) - [x] [Cache CARGO_ environment variables](https://github.com/mozilla/sccache/issues/89)
