chore(ci): use GitHub Actions to run unit tests on Windows and macOS

[mathiasbynens]

Similar to our earlier Travis CI setup, we continue to run exhaustive checks on Linux, while also verifying the build + unit tests still work on other platforms.

Issue: #6726

[jschfflr]

LGTM % question.
Is there also maybe a way to define the common steps just once?

[mathiasbynens]

Is there also maybe a way to define the common steps just once?

I initially tried doing that with needs: but it got a little unwieldy pretty fast. IMHO this is a case where it's more readable/maintainable to have a small amount of duplication.

[jschfflr]

Sounds good, thanks!

[mathiasbynens]

Maksim, could you also PTAL?

[sadym-chromium]

Is there also maybe a way to define the common steps just once?

I initially tried doing that with needs: but it got a little unwieldy pretty fast. IMHO this is a case where it's more readable/maintainable to have a small amount of duplication.

I have the same concern about having lots of copy-pasted code. But if the needs implementation is even more bulky, let's stick to this one for now.

[sadym-chromium]

Do we need to add those jobs somewhere, or they all of them run automatically in workflows?

[mathiasbynens]

Do we need to add those jobs somewhere, or they all of them run automatically in workflows?

They're all run automatically.

[sadym-chromium]

LGTM