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