GitHub Actions: Add builds using cmake. (#231)

.github/workflows/build.yml

@@ -29,3 +29,26 @@ jobs:
       - name: Build
         working-directory: bin
         run: ./makeright x
+
+  build-cmake:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [macos-11.0, macos-10.15, ubuntu-20.04, ubuntu-18.04]
+    env:
+      BUILD_TYPE: Release
+    steps:
+    - uses: actions/checkout@v2
+    - name: Install X11 dependencies on MacOS
+      if: ${{ runner.os == 'macOS'}}
+      run: brew install --cask xquartz
+    - name: Create Build Environment
+      run: cmake -E make_directory ${{github.workspace}}/build
+    - name: Configure CMake
+      shell: bash
+      working-directory: ${{github.workspace}}/build
+      run: cmake $GITHUB_WORKSPACE -DCMAKE_BUILD_TYPE=$BUILD_TYPE
+    - name: Build
+      working-directory: ${{github.workspace}}/build
+      shell: bash
+      run: cmake --build . --config $BUILD_TYPE