[clang] [Clang][Driver] Fix compiler-rt library directory for cygwin (PR #208925)

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tyan0 wrote:

I have added a test. SInce the test needs https://github.com/llvm/llvm-project/pull/147960, so I rebased this branch onto the top of https://github.com/llvm/llvm-project/pull/147960. As a result, this PR looks to contain https://github.com/llvm/llvm-project/pull/147960. What should I do?

https://github.com/llvm/llvm-project/pull/208925