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

[Tomohiro Kashiwada via cfe-commits]

kikairoya wrote:

> I have added a test. Since the test needs #147960, so I rebased this branch onto the top of #147960. As a result, this PR looks to contain #147960. What should I do?

You can test this with `-print-file-name` and `-print-runtime-dir`, like  https://github.com/llvm/llvm-project/commit/1971823ecb9eaa077554a5d268a44c7cb75eccce, without the linker invocation changes.
Some dummy files would be needed in `Inputs/resource_dir` and maybe `Inputs/resource_dir_with_per_target_subdir`.

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