anchor.diff:   *  External libraries
    */
   assert flite != null -> alsa-lib != null;
  -assert libxcbshmExtlib -> xorg.libxcb != null;
  -assert libxcbxfixesExtlib -> xorg.libxcb != null;
  -assert libxcbshapeExtlib -> xorg.libxcb != null;
  +assert libxcbshmExtlib -> libxcb != null;
  +assert libxcbxfixesExtlib -> libxcb != null;
  +assert libxcbshapeExtlib -> libxcb != null;
   assert gnutls != null -> openssl == null;
   assert openssl != null -> gnutls == null;
   
  
positive.code:     "--${boolEn (x264 != null)}-libx264"
      "--${boolEn (x265 != null)}-libx265"
      "--${boolEn (xavs != null)}-libxavs"
      #"--${boolEn (xorg.libxcb != null)}-libxcb"
      "--${boolEn libxcbshmExtlib}-libxcb-shm"
      "--${boolEn libxcbxfixesExtlib}-libxcb-xfixes"
      "--${boolEn libxcbshapeExtlib}-libxcb-shape"
  
negative.code:     libvorbis
      libvpx
      libwebp
      libx11
      libxcb
      libxext
      libxfixes
      libxml2
      libxv
      #xorg.libXvMC
      mfx-dispatcher
      nvidia-cuda-toolkit
      nvidia-drivers
  