Support for trybuild and similar macro testing tools

[neysofu]

https://github.com/dtolnay/trybuild is a Rust testing utility that invokes rustc on user-provided source files and tests whether they run successfully or fail to compile. Given how popular it is in the ecosystem, and how easy it would be to support it, I think it makes sense to introduce some logic to handle this correctly. This PR adds support for trybuild and a few other crates in the category:

• target/tests/target for kaos and macrotest;
• target/tests/trybuild for trybuild.

As far as I know tests is not used by any other popular crates, so there should be no conflicts. These are quite ordinary nested target directories and the code changes are trivial. I might need some help with the testing, though – not sure how the current setup works. I'm allowing edits by maintainers so you can push directly to this branch, if you so prefer, I don't mind.

Relevant issues in other repositories:

• Program macro to generate helper fns and documentation solana-labs/solana#10826
• Investigate why CI doesn't cache trybuild dependencies Sovereign-Labs/sovereign-sdk#735 (that's me!)

Thank you so much for the action, by the way! I use it a bunch 😄

[neysofu]

Hi @Swatinem, let me know if I can assist with the review in any way! 😄

[Swatinem]

I believe that should do the trick.
There isn’t really a lot of testing going on with rust-cache except running various cargo test variants to see if things are properly cached or not.

[neysofu]

Thanks for the review! I had to fix CI (forgot to run npm run prepare), should pass now.

[Swatinem]

However the caching does not fully work I believe:
https://github.com/Swatinem/rust-cache/actions/runs/6162180271/job/16723178553?pr=168
This is still compiling the world as part of the trybuild test.

[neysofu]

I suspect it's because the first run didn't include the changes to dist/, so it deleted tests/trybuild resulting in a rebuild.

Can we try deleting the cache and doing 2 runs of simple.yml (one uncached and the other hopefully cached)? If we still see a re-build then yeah, we have a problem.

[Swatinem]

Oh yeah indeed, that would explain it.

Let me delete the cache and rerun this as you suggested.

[Swatinem]

Works like a charm, thanks!