Move CI to github action

[bowenwang1996]

Looks like github action supports caching now https://github.com/actions/cache. We should try again to see if it works for us now.

[ailisp]

2gb is possibly too limited for rust. Will still give a try if it gives a reasonable speedup:
https://help.github.com/en/actions/automating-your-workflow-with-github-actions/caching-dependencies-to-speed-up-workflows#usage-limits-and-eviction-policy

[bowenwang1996]

Does using our own runner solve this problem? https://help.github.com/en/actions/automating-your-workflow-with-github-actions/hosting-your-own-runners

[ailisp]

It's undocumented whether self hosted runner support a customized maximum cache, but i can try
Update: tried, looks it's not configurable. i contact github team and see if it's possible

[ilblackdragon]

@ailisp Given you switched to buildkite - I'm assuming this can be closed?

[ailisp]

Yes