Recent `cc` causes macos build failure

When we do a cargo update, the MacOS build breaks. See !2231 (closed), !2234 (merged), !2300 (merged).

The current workaround is to do a little dance to avoid updating it in our Cargo.lock. This isn't great, because it tends to get in the way of releasing, and because any users actually on MacOS might be afflicted.

I've filed an upstream ticket https://github.com/rust-lang/cc-rs/issues/1170