[rust] Add CI Checks to Rust fork

[dianqk]

• On Linux, run check-llvm and check-lld.
• On macOS, run check-llvm.

I haven't added it on Windows yet, as I haven't been able to get it working with the free tier of GitHub Actions.

[cuviper]

Is there precedent for using these actions in other rust-lang projects?

• jlumbroso/free-disk-space
• hendrikmuhs/ccache-action

I see the latter is used by LLVM already, but pinned to a specific commit, which is prudent since tags can change -- and this was a recent vulnerability in a popular action, in case you missed it.

[dianqk]

Is there precedent for using these actions in other rust-lang projects?

• jlumbroso/free-disk-space
• hendrikmuhs/ccache-action

I see the latter is used by LLVM already, but pinned to a specific commit, which is prudent since tags can change -- and this was a recent vulnerability in a popular action, in case you missed it.

Thanks! For the former, I would use https://github.com/rust-lang/rust/blob/master/src/ci/scripts/free-disk-space.sh.

[nikic]

As this is a read-only action in a repo that never produces any artifacts, we probably don't need to be overly concerned with GHA security?

[cuviper]

As this is a read-only action in a repo that never produces any artifacts, we probably don't need to be overly concerned with GHA security?

I suppose you're right, but it doesn't hurt to be a little cautious in case that ever changes.