* Initial version of release workflow using GitHub Actions
Add release workflow using GitHub Actions to replace the current Azure
DevOps pipeline. Currently the same functionality is implemented. This
uses multiple builds in parallel to make better use of CPU resources.
Remove Azure DevOps pipeline.
* Add GitHub Actions workflow for pull-request checks
Lint Dockerfile and shell scripts when PRs are opened.
* Use multiple runners in parallel
Buildroot has stretches where CPU resources are not fully utilized.
Spawn multiple builds accross builders to increase load. Also sort them
by architecture to maximize ccache hit rate.
* Checkout before validate version
3f5b28a0b4