[llvm] [Support] Add option to use Windows vendored ICU (PR #186371)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `intel-sycl-gpu` running on `intel-sycl-gpu-01` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/225/builds/3870

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

```
Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'libomp :: tasking/omp_fill_taskqueue.c' FAILED ********************
Exit Code: 255

Command Output (stdout):
--
# RUN: at line 1
/home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/./bin/clang -fopenmp   -I /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/src -I /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/openmp/runtime/test -L /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/src  -fno-omit-frame-pointer -I /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/openmp/runtime/test/ompt /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/openmp/runtime/test/tasking/omp_fill_taskqueue.c -o /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/omp_fill_taskqueue.c.tmp -lm -latomic && env KMP_ENABLE_TASK_THROTTLING=0 /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/omp_fill_taskqueue.c.tmp
# executed command: /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/./bin/clang -fopenmp -I /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/src -I /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/openmp/runtime/test -L /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/src -fno-omit-frame-pointer -I /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/openmp/runtime/test/ompt /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/llvm-project/openmp/runtime/test/tasking/omp_fill_taskqueue.c -o /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/omp_fill_taskqueue.c.tmp -lm -latomic
# executed command: env KMP_ENABLE_TASK_THROTTLING=0 /home/test-user/llvm-buildbot-worker/intel-sycl-gpu/build/runtimes/runtimes-bins/openmp/runtime/test/tasking/Output/omp_fill_taskqueue.c.tmp
# note: command had no output on stdout or stderr
# error: command failed with exit status: 255

--

********************


```

</details>

https://github.com/llvm/llvm-project/pull/186371