CI: add windows ubsan and clang workflows

[mizvekov]

No description provided.

[mizvekov]

FYI this is why the clang-windows job is failing: #4139

[vtjnash]

Does it work with #4185 now?

[mizvekov]

@vtjnash I just rebased, but this was no-test. There is something different with the MSVC CI now, compared to last month, where before 'Ninja' tool was available, now is not.
So we are failing before we even try to generate the build system, which does not test your changes.

[mizvekov]

@vtjnash Looks good now, we generate a valid ninja.build, which gets us farther than before.

Now it's failing still, for a different reason, not the one I intended originally. It's the same problem as this: microsoft/STL#3568
This issue is easy to work around though, there is a clang flag which makes the sanitizer CodeGen just emit traps instead of calls to the ubsan runtime. I will make this change soon enough, it's getting late here.

After that is working, I would expect this CI job to fail once again, but this time due to UB when running the windows tests, which is what I intended to demonstrate initially.

[mizvekov]

Alright, thanks for the review!
You can go ahead and merge this.