Add GitHub action for running libclc tests

Author: tstellar

.github/workflows/libclc-tests.yml

@@ -0,0 +1,53 @@
+name: libclc Tests
+
+on:
+  push:
+    branches:
+      - 'release/**'
+    paths:
+      - 'clang/**'
+      - 'llvm/**'
+      - 'libclc/**'
+      - '.github/workflows/libclc-tests.yml'
+  pull_request:
+    paths:
+      - 'clang/**'
+      - 'llvm/**'
+      - 'libclc/**'
+      - '.github/workflows/libclc-tests.yml'
+
+jobs:
+  build_libclc:
+    name: libclc test 
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - ubuntu-latest
+          # Disable build on windows, because I can't figure out where llvm-config is.
+          #- windows-latest
+          - macOS-latest
+    steps:
+    - name: Setup Windows
+      if: startsWith(matrix.os, 'windows')
+      uses: llvm/actions/setup-windows@master
+      with:
+        arch: amd64
+    - name: Install Ninja
+      uses: llvm/actions/install-ninja@master
+    - uses: actions/checkout@v1
+      with:
+        fetch-depth: 1
+    - name: Build clang
+      uses: llvm/actions/build-test-llvm-project@master
+      with:
+        cmake_args: -G Ninja  -DLLVM_ENABLE_PROJECTS="clang" -DCMAKE_BUILD_TYPE=Release
+        build_target: ""
+    - name: Build and test libclc
+      run: |
+        mkdir libclc-build
+        cd libclc-build
+        cmake -G Ninja ../libclc -DLLVM_CONFIG=../build/bin/llvm-config
+        ninja
+        ninja test