Create GitHub Action workflow for building project on Windows, Linux and macOS

[pbek]

This could serve as start for CI and later even release building and deploying for all platforms (not just Windows).
The workflow would be run on all branches and for all pull requests.

[pbek]

I lately also migrated my https://github.com/pbek/QOwnNotes away from AppVeyor and TravisCI for CI and release building. GitHub Actions are so much more convenient and faster. And you can serve all three platforms at the same time.

[pbek]

For QOwnNotes I also build releases for all three platforms that result in a single GitHub release with a ZIP for Windows, an AppImage for Linux and a DMG for macOS.

See: https://github.com/pbek/QOwnNotes/blob/develop/.github/workflows/build-release.yml

[pbek]

The workflow for this PR builds for all three platform, see https://github.com/pbek/opentrack/actions/runs/209854964

[Slion]

That is what we need. Would be great if we could download the resulting Windows installer once the build is finished.

[Cat-Lady]

Any progress on merging this, after... 4 years?

[sthalik]

On OSX it's missing dependencies such as foohid. On Windows attempts at automated builds won't be enough until the move to Qt 6 when it can finally be included as a submodule. If you want to help with builds then try getting CI to pick up the non-public depends-nonfree repo in read-only mode.

The state of OSX builds has improved since @rvt's commits and my windeployqt fix from #1705.