anchor.diff:  { lib
   , stdenv
   , fetchFromGitHub
  +, fetchurl
   , autoconf
   , automake
   , fontconfig
  
positive.code:     libX11 # tcltk
      tcl
      tk
      xorg.libXft
      zlib
    ];
  
negative.code: 
    postUnpack = ''
      mkdir -p $sourceRoot/src/vendor/yices/v2.6/yices2
      tar -C $sourceRoot/src/vendor/yices/v2.6/yices2 -xf ${yices-src}
      chmod -R +rwX $sourceRoot/src/vendor/yices/v2.6/yices2
    '';
  
  