message: Update github action to trigger defines via CMake
  Use options via explicit CMake defines, instead of calling them from
  the generic PUGI_BUILD_DEFINES variable.
diff: @@ -42,7 +42,7 @@ jobs:
  steps:
  - uses: actions/checkout@v1
  - name: cmake configure
  - run: cmake . -DPUGIXML_BUILD_TESTS=ON -DPUGIXML_BUILD_DEFINES=${{matrix.defines}} -A ${{matrix.arch}}
  + run: cmake . -DPUGIXML_BUILD_TESTS=ON -D${{matrix.defines}}=ON -A ${{matrix.arch}}
  - name: cmake test
  shell: bash # necessary for fail-fast
  run: |
  