[CI] Install msvc build tools

.github/workflows/cmake.yml

@@ -18,6 +18,7 @@ jobs:
     - uses: actions/checkout@v2
       with:
         submodules: recursive
+    - uses: ilammy/msvc-dev-cmd@v1
     - name: SetupRust
       uses: dtolnay/rust-toolchain@stable
     - name: Install LLVM
@@ -39,7 +40,7 @@ jobs:
       # Note the current convention is to use the -S and -B options here to specify source 
       # and build directories, but this is only available with CMake 3.13 and higher.  
       # The CMake binaries on the Github Actions machines are (as of this writing) 3.12
-      run: cmake $GITHUB_WORKSPACE -GNinja -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DRust_CARGO_TARGET=x86_64-pc-windows-msvc -DCMAKE_C_COMPILER=clang-cl -DCMAKE_CXX_COMPILER=clang-cl
+      run: cmake $GITHUB_WORKSPACE -GNinja -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DRust_CARGO_TARGET=x86_64-pc-windows-msvc -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
 
     - name: Build
       working-directory: ${{github.workspace}}/build