[llvm] [LLVM][TargetParser] Handle -msys targets the same as -cygwin. (PR #136817)

[via llvm-commits]

jeremyd2019 wrote:

Notably, the msys triple is generated by the config.guess in this repo via llvm/modules/GetHostTriple.cmake: https://github.com/llvm/llvm-project/blob/da8f2d52423bb82b5d4e75cff3018704effe044f/llvm/cmake/config.guess#L809-L811

https://github.com/llvm/llvm-project/pull/136817