anchor.diff:  /*
    *  External libraries
    */
  -#assert decklinkExtlib ->
  -#  blackmagic-design-desktop-video != null
  -#  && multithreadBuild;
  -assert faacExtlib -> faac != null;
  -assert fdkaacExtlib -> fdk_aac != null;
  -assert gnutls != null -> !opensslExtlib;
   assert libxcbshmExtlib -> xorg.libxcb != null;
   assert libxcbxfixesExtlib -> xorg.libxcb != null;
   assert libxcbshapeExtlib -> xorg.libxcb != null;
  -assert nvencExtLib -> nvidia-video-codec-sdk != null;
  -assert opensslExtlib ->
  -  gnutls == null
  -  && openssl != null;
  +assert gnutls != null -> openssl == null;
  +assert openssl != null -> gnutls == null;
   assert x11grabExtlib ->
     xorg.libX11 != null
     && xorg.libXv != null;
  
positive.code:  */
  # GPL
  assert
    fdkaacExtlib
    #|| avid != null
    #|| cdio != null
    || frei0r-plugins != null
    || opensslExtlib
    || rubberband != null
    || samba_client != null
    #|| utvideo != null
  
negative.code:     /**/(fflag "--disable-libnpp" "3.1")
      #"--${boolEn (mmal != null)}-mmal"
      /**/"--disable-mmal"
      "--${boolEn (nvidia-video-codec-sdk != null)}-nvenc"
      "--${boolEn (libva != null)}-vaapi"
      "--disable-vda" # darwin
      "--${boolEn (libvdpau != null)}-vdpau"
  