anchor.diff:  
   RUN update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-7 90
   RUN update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 90
  -RUN DEBIAN_FRONTEND=noninteractive apt-get install -y gstreamer1.0-libav
   RUN mkdir -p /app
   
   ADD . /app
  
positive.code:     rm -r spdlog-${SPDLOG} && \
      rm spdlog.tar.gz
  
  RUN curl -o /root/cmake.tar.gz https://cmake.org/files/v3.10/cmake-${CMAKE}.tar.gz && \
  	cd /root && \
      tar -zxvf cmake.tar.gz && \
      cd cmake-${CMAKE} && \
      cmake . && \
  
negative.code: 
  RUN ACLOCAL_PATH="/usr/local/share/aclocal" && \
      export ACLOCAL_PATH && \
      curl -o /root/libsigcplusplus.tar.gz -SL https://github.com/GNOME/libsigcplusplus/archive/${SIGC}.tar.gz && \
      cd /root && \
      tar -zxvf libsigcplusplus.tar.gz && \
      cd libsigcplusplus-${SIGC} && \
  