[clang] [clang][unittests] Build the libclang unit tests on Windows (PR #232809)

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UebelAndre wrote:

This change is in response to discussions on https://github.com/llvm/llvm-project/pull/228405. The change aims to confirm the behavior of the clang unit tests for windows.

https://github.com/llvm/llvm-project/pull/232809