[clang] Remove Linux search paths on Windows (PR #113628)

[Joseph Huber via cfe-commits]

https://github.com/jhuber6 commented:

Is there an issue with simply using the `HostTC` for everything? I feel like that's the solution to this mess, since the `HostTC` would always know whether or not the target is Windows without us needing to forward a bunch of stuff. 

https://github.com/llvm/llvm-project/pull/113628