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

[via cfe-commits]

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.
> 
> I think there may be a misunderstanding here. Because the wording of your PR sounds a bit like clang-cl and winsysroot are bad and should be wiped out. But in reality, you just added a new feature for clang --target=*-pc-windows-msvc that does not change or break the behavior of clang-cl and winsysroot.
> 
> As long as the sysroot generator is supported, I don't think it does anyone any harm.

When did i argue clang-cl is evil? /winsysroot is a clang-cl toggle and it has nothing to do with --sysroot=.

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