[clang] [clang] Support --sysroot= for ${arch}-windows-msvc targets (PR #96417)

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trcrsired wrote:

> You can't deny the existence of economics. Large companies like Google have indeed contributed the most to LLVM, which determines their dominance.
> 
> >

That does not mean small developers like me should be bullied either which is exactly what antitrust law is supposed to protect.

https://github.com/llvm/llvm-project/pull/96417