[libclc] [llvm] [libclc][CMake] Use clang/llvm-ar on Windows (PR #186726)

[LLVM Continuous Integration via cfe-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `clang-s390x-linux-lnt` running on `systemz-1` while building `libclc,llvm` at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/136/builds/7080

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 7 (ninja check 1) failure: stage 1 checked (failure)
...
    put((job, i, (False, wrapped)))
  File "/usr/lib/python3.10/multiprocessing/queues.py", line 377, in put
    self._writer.send_bytes(obj)
  File "/usr/lib/python3.10/multiprocessing/connection.py", line 200, in send_bytes
    self._send_bytes(m[offset:offset + size])
  File "/usr/lib/python3.10/multiprocessing/connection.py", line 411, in _send_bytes
    self._send(header + buf)
  File "/usr/lib/python3.10/multiprocessing/connection.py", line 368, in _send
    n = write(self._handle, buf)
BrokenPipeError: [Errno 32] Broken pipe
FAILED: CMakeFiles/check-all /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/CMakeFiles/check-all 
cd /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1 && /home/uweigand/sandbox/bin/python3.10 /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/./bin/llvm-lit -v -j4 /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/utils/mlgo-utils /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/tools/clang/tools/extra/include-cleaner/test /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/tools/clang/tools/extra/clangd/test/../unittests /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/tools/clang/tools/extra/clangd/test /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/tools/clang/tools/extra/test /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/tools/clang/test @/home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/runtimes/runtimes-bins/lit.tests /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/utils/lit /home/uweigand/sandbox/buildbot/clang-s390x-linux-lnt/stage1/test
ninja: build stopped: subcommand failed.

```

</details>

https://github.com/llvm/llvm-project/pull/186726