Reuse Agent artifacts if nothing in src/agent changes

[Porges]

The agent build takes most of the CI runtime, so improve it by only rebuilding if the pre-reqs or something inside src/agent changes.

[Porges]

We should probably build the Rust version into the cache key for both this and the pre-reqs.

[tevoinea]

If I remember correctly, the check-pr pipeline pulls down the github actions artifacts when testing against a PR. We should make sure this doesn't break that flow. I do see artifacts published at the end of the actions run so it might 'just work'.

[Porges]

If I remember correctly, the check-pr pipeline pulls down the github actions artifacts when testing against a PR. We should make sure this doesn't break that flow. I do see artifacts published at the end of the actions run so it might 'just work'.

Yes, the artifacts are still downloaded and packaged into the release zip, so it should work the same as before.

[Porges]

We should probably build the Rust version into the cache key for both this and the pre-reqs.

This is done now.

[Porges]

Running one more check-pr to ensure this didn't break anything.

[Porges]

One thing to think about is that the version number in the compiled binary might be wrong. Need to disable this cache on builds from a specific tag.

[Porges]

One thing to think about is that the version number in the compiled binary might be wrong. Need to disable this cache on builds from a specific tag.

This is done now.

[Porges]

Cleanly passed check-pr.

[Porges]

Hold off on merging as I think we still have a problem with the version check in the API service, which will try to reimage the nodes if they don't have an exact version match.

[Porges]

We now set ONEFUZZ_ALLOW_OUTDATED_AGENT during check-pr to allow the use of older versions.