Auto merge of #1932 - JohnTitor:harden-builds, r=JohnTitor

Add some more targets for build testing

- `x86_64-unknown-illumos`: We now have the illumos module and it'd be great if we could test it actually.
- `aarch64-apple-darwin`: This target will be used more widely in the future and it should make sense to run CI for it as well.