[llvm] [Offload] Enable offload test on Windows (PR #212480)

[Nick Sarnie via llvm-commits]

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sarnex wrote:

maybe we could reword it a little?
```suggestion
  message(STATUS "Skipping libomptarget lit suites because libomptarget was not built.")
```

https://github.com/llvm/llvm-project/pull/212480