[clang] [Driver] Remove a bunch of unnecessary REQUIRES constraints (PR #94055)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> > The best I can do is mark them UNSUPPORTED: system-windows to get the bots green again.
> 
> This is not a good idea. You will disable these tests for the appropriate cross builders for no reason and they will became useless for them. I would strongly recommend to revert #94253 and assign the correct target requirements for the failed tests (or restore the previous ones).

@vvereschaka  `// UNSUPPORTED: system-windows` was a fairly reasonable workaround, after the previously imprecise `// REQUIRES: x86-registered-target` had been removed. (It seems that there is an arm/aarch64 window bot that does not enable x86 targets.)

#94276 seems to fix the test properly.

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I think requiring all driver tests pass with a custom `DEFAULT_SYSROOT` is an undue burden.
Do you know why llvm-zorg/buildbot/osuosl/master/config/builders.py llvm-clang-win-x-aarch64 needs to set `DEFAULT_SYSROOT`?
I think it should migrate to https://clang.llvm.org/docs/UsersManual.html#configuration-files instead.


https://github.com/llvm/llvm-project/pull/94055