message: GH-actions: multiple OS'.
  Now using `cmake` calls instead of shellscripts.
diff: @@ -2,22 +2,37 @@ name: Ubuntu CI
  on: [push]
  +env:
  + BUILD_TYPE: Release
  +
  jobs:
  build:
  - runs-on: ubuntu-latest
  + runs-on: ${{ matrix.config.os }}
  + strategy:
  + matrix:
  + config:
  + - os: ubuntu-latest
  + - os: macos-latest
  + - os: windows-latest
  steps:
  - uses: actions/checkout@v2
  + - name: Create build folder
  + run: cmake -E make_directory ${{runner.workspace}}/build
  +
  - name: configure
  shell: bash
  - run: ./cmake.sh
  + working-directory: ${{runner.workspace}}/build
  + run: cmake $GITHUB_WORKSPACE -DCMAKE_BUILD_TYPE=$BUILD_TYPE
  - name: build
  shell: bash
  - run: ./make.sh
  + working-directory: ${{runner.workspace}}/build
  + run: cmake --build . --config $BUILD_TYPE
  - name: test
  shell: bash
  - run: ./ctest.sh
  \ No newline at end of file
  + working-directory: ${{runner.workspace}}/build
  + run: ctest --output-on-failure
  \ No newline at end of file
  