anchor.diff:  { lib
   , stdenv
   , fetchsvn
  -, pkgconfig
  +, pkg-config
   , libjpeg
   , libpng
   , flex
  
positive.code:     sha256 = "1m7ks6k53gsjsdazgf22g16dfgj3pqvqy9mhxzlwszv5808sj5w5";
    };
  
    postPatch = ''
      # Install libnetpbm.so symlink to correct destination
      substituteInPlace lib/Makefile \
        --replace '/sharedlink' '/lib'
    '';
  
    nativeBuildInputs = [
      pkgconfig
      flex
      makeWrapper
    ];
  
negative.code: 
      runHook postConfigure
    '';
  
    installPhase = ''
      runHook preInstall
  