cmake HAVE_OGG_VORBIS examples

longturn/freeciv21 cmake/FreecivDependencies.cmake :164 

check_source_runs(CXX [[
      #include <QMediaFormat>
      int main() {
        auto fmt = QMediaFormat(QMediaFormat::Ogg);
        fmt.setAudioCodec(QMediaFormat::AudioCodec::Vorbis);
        return fmt.isSupported(QMediaFormat::Decode) ? 0 : 1;
      }
      ]]
      HAVE_OGG_VORBIS)