anchor.diff:  
     nativeBuildInputs = [ pkg-config cmake ];
     buildInputs = [
  -    readline uthash woff2 zeromq libuninameslist
  +    readline uthash woff2 zeromq
       python freetype zlib glib giflib libpng libjpeg libtiff libxml2
     ]
       ++ lib.optionals withSpiro [ libspiro ]
  
positive.code: 
  stdenv.mkDerivation rec {
    pname = "fontforge";
    version = "20201107";
  
    src = fetchFromGitHub {
      owner = pname;
      repo = pname;
      rev = version;
      sha256 = "sha256-Rl/5lbXaPgIndANaD0IakaDus6T53FjiBb45FIuGrvc=";
    };
  
    patches = [
  
negative.code: { stdenv, fetchpatch, fetchFromGitHub, lib
  , cmake, perl, uthash, pkg-config, gettext
  , python, freetype, zlib, glib, giflib, libpng, libjpeg, libtiff, libxml2, cairo, pango
  , readline, woff2, zeromq
  , withSpiro ? false, libspiro
  , withGTK ? false, gtk3
  , withGUI ? withGTK
  