Add Windows Clang workflow to nightly matrix

[henderkes]

As requested here: #21619 (comment)

I am not sure if 8.2 actually builds with Clang or if I need to pick some other fixes from above mentioned branch in here, too.
@iluuu1994 could you add the CI: Windows label?

[iluuu1994]

Great, thanks! I added the labels, you'll need to push again for CI to pick up on it.

[iluuu1994]

To stay consistent with the other jobs, this should be enabled only with $all_variations but not with $test_windows.

[henderkes]

I would like there to be a simple path to testing windows+clang. Generally every change affecting Windows should work on both MSVC and Clang. Would you be open to a different label instead?

[iluuu1994]

What's the intention of the label? To run the Window+Clang build only without running the other Windows builds?

[henderkes]

Thinking about it again, a new label doesn't make sense. I just believe Clang should always be tested and eventually become the default. It's just producing so much faster binaries.

[iluuu1994]

Ok. Please make the changes as suggested for now. We can reconsider enabling it by-default if they become the default. I doubt Clang builds on Windows are in wide use atm. If you push with the suggested changes, the job should run.

[iluuu1994]

Oh sorry, I see that you already made this change. I'll see how we should proceed.

[henderkes]

Already done as suggested

if the windows team doesn't want to switch to clang for 8.6 yet, we might ship clang builds with FrankenPHP as an alternative build. If it were 10% performance there'd be no reason, but +60-90% faster is just hard to ignore. No enhancement we could ever do to FrankenPHP itself could offer that much extra performance