[llvm] Build clang with the latest released clang on Windows on Arm. (PR #116701)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

> [2] `cmake -G Ninja -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_PROJECTS="clang;lld" -DLLVM_ENABLE_RUNTIMES="compiler-rt" -DLLVM_TARGETS_TO_BUILD="AArch64" -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF ../llvm && ninja clang compiler-rt`

In addition to the other request to clarify the wording of the commit message, I think it would be good to spell out the implicit details here; configuring like this, without explicitly telling CMake to use `clang-cl`, will make it pick the GNU style `clang` driver, and compiling in MSVC mode with the GNU style driver is generally a less tested configuration.

https://github.com/llvm/llvm-project/pull/116701