Migrate to GitHub actions

[pragmatrix]

Update 20210612:

• We can't wait any longer for several reasons:
  • The Azure 10GB storage limitations are affecting us.
  • GitHub Actions support Big Sur Images we need to cross compile for M1 machines.

The idea now is to create a Rust program that creates the workflows based on some simple templates.

• Compile Host Targets
• Clippy
• Generate and upload artifacts
• Android & iOS targets
• Resolver v2
• Release builds
  • How should they be organized, a separate set of workflows that run only on the release branch, or should we just create all jobs and somehow filter them by branch?
  • push releases.
• Use sccache?

  Too much work for now, may be later: https://www.infinyon.com/blog/2021/04/github-actions-best-practices/

• Nightly QA builds.

Update 20200826:

Waiting for support to run local and regular actions from local actions:

• Next Steps for Fully Functioning Composite Actions actions/runner#646
• (In Progress) Composing Actions Within Actions Proof of Concept actions/runner#612