Replace actions/checkout with actions/upload/download

[alpeb]

So far just a test, please don't review

[alpeb]

@siggy this is ready for review. I've removed all the action/checkout entries except for the one at the top. It ended up in quite a lot of repetitions, but I don't know if there's anything we can do about it. Let me know what you think.

[siggy]

awesome to see this!

i wouldn't worry too much about the repetition. we already have a lot of that. eventually we could move the repeated bits into their own actions, or wait for yaml anchor support.

the current test failure looks related to a dirty repo.

browsing through a couple stack overflow questions, it sounds like copying a git repo is not a great idea. instead, we could just tar and upload the .git directory, download it to a temp location (i think {{ runner.temp }} or $RUNNER_TEMP will work?), and then git clone {{ runner.temp }} {{ github.workspace }}

[alpeb]

@siggy this is ready for review again. The tests were green!

[siggy]

Very excited to see this, great work! ✅ ✅ ✅

[alpeb]

Notes for reviewers:

This replaces the multiple calls to actions/checkout as a workaround to actions/checkout#27
With this PR, there's a new download_src job at the beginning that calls actions/checkout, tars the .git directory and then uploads it into the builds' artifact storage using actions/upload-artifact.

Ever other job depends on download_src. Now instead of calling actions/checkout again, they use actions/download-artifact to download the tarball, untar it into the runner's temporary storage dir, and clone from it into the workspace.

[ihcsim]

Thanks for fixing this 👍.