If gems don't exist as precompiled versions for linux and/or mac then allow bundler to compile them instead.

Without this it constantly gets added anytime you run bundler on a mac, won't affect production but means developers on macs don't have issues.

Generated by running
    $ bundle lock --add-checksums
These are updated whenever bundler adds or updates a gem in our dependencies, and ensures if a gem changes upstream after we've initially pinned it then we can detect it. (eg, someone changes the .gem file for a given version of a gem.) It's a mitigation against a supply chain attack.

caius marked this pull request as ready for review