Add more compilers (#307)

.github/workflows/cmake.yml

@@ -21,15 +21,16 @@ jobs:
 
     strategy:
       matrix:
-        os: [ubuntu-18.04, ubuntu-20.04]
-
+        os: [ubuntu-18.04]
+        compiler: [g++-7, g++-9, g++-10, clang++]
+         
     steps:
     - uses: actions/checkout@v2
 
     - name: Configure CMake
       # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.
       # See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html?highlight=cmake_build_type
-      run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}
+      run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_CXX_COMPILER=${{matrix.compiler}}
 
     - name: Build
       # Build your program with the given configuration