Update GitHub Actions workflow (#315)

.github/workflows/cmake.yml

@@ -3,15 +3,10 @@ name: CMake
 on: [push, pull_request]
 
 env:
-  # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
   BUILD_TYPE: Release
 
 jobs:
   build:
-    # The CMake configure and build commands are platform agnostic and should work equally
-    # well on Windows or Mac.  You can convert this to a matrix build if you need
-    # cross-platform coverage.
-    # See: https://docs.github.com/en/actions/configuring-and-managing-workflows/configuring-a-workflow#configuring-a-build-matrix
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -20,30 +15,22 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
-    - name: Create Build Environment
-      # Some projects don't allow in-source building, so create a separate build directory
-      # We'll use this as our working directory for all subsequent commands
-      run: cmake -E make_directory ${{runner.workspace}}/build
-
     - name: Configure CMake
-      # Use a bash shell so we can use the same syntax for environment variable
-      # access regardless of the host operating system
-      shell: bash
-      working-directory: ${{runner.workspace}}/build
-      # 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 $GITHUB_WORKSPACE -DCMAKE_BUILD_TYPE=$BUILD_TYPE
+      run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}
 
     - name: Build
-      working-directory: ${{runner.workspace}}/build
-      shell: bash
-      # Execute the build.  You can specify a specific target with "--target <NAME>"
-      run: cmake --build . --config $BUILD_TYPE
+      run: cmake --build ${{github.workspace}}/build --config ${{env.BUILD_TYPE}}
 
     - name: Test
-      working-directory: ${{runner.workspace}}/build
-      shell: bash
-      # Execute tests defined by the CMake configuration.
-      # See https://cmake.org/cmake/help/latest/manual/ctest.1.html for more detail
-      run: ctest -C $BUILD_TYPE --output-on-failure
+      working-directory: ${{github.workspace}}/build
+      run: ctest -C ${{env.BUILD_TYPE}}
+
+    - name: Configure CMake with C++20
+      run: cmake -B ${{github.workspace}}/build_20 -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_CXX_STANDARD=20
+
+    - name: Build with C++20
+      run: cmake --build ${{github.workspace}}/build_20 --config ${{env.BUILD_TYPE}}
+
+    - name: Test with C++20
+      working-directory: ${{github.workspace}}/build_20
+      run: ctest -C ${{env.BUILD_TYPE}}