feat: install llvm on macOS

Author: XuehaiPan

.github/workflows/ci.yml

@@ -226,9 +226,14 @@ jobs:
             echo "PIP_EXTRA_INDEX_URL=${PIP_EXTRA_INDEX_URL}" | tee -a "${GITHUB_ENV}"
             echo "UV_INDEX=${UV_INDEX}" | tee -a "${GITHUB_ENV}"
           fi
+
+          brew update
+          brew list --formula llvm || brew install llvm
+          export PATH="$(brew --prefix llvm)/bin:${PATH}"
           export CLANG_TIDY_CMAKE_OPTIONS="${CLANG_TIDY_CMAKE_OPTIONS} -DUSE_METAL=ON"
 
           echo "USE_METAL=ON" | tee -a "${GITHUB_ENV}"
+          echo "PATH=${PATH}" | tee -a "${GITHUB_ENV}"
           echo "CLANG_TIDY_CMAKE_OPTIONS=${CLANG_TIDY_CMAKE_OPTIONS}" | tee -a "${GITHUB_ENV}"
 
       - name: Setup Python and uv with caching