anchor.diff:      license = licenses.zlib;
       platforms = platforms.all;
     };
  -} // (if stdenv.isDarwin then {
  -  postInstall = ''
  -    # jww (2015-01-06): Sometimes this library install as a .so, even on
  -    # Darwin; others time it installs as a .dylib.  I haven't yet figured out
  -    # what causes this difference.
  -    for file in $out/lib/*.so* $out/lib/*.dylib* ; do
  -      install_name_tool -id "$file" $file
  -    done
  -  '';
  -} else {}))
  +}
  +
  
positive.code:   outputs = [ "dev" "out" "static" "man" ];
    setOutputFlags = false;
  
    configureFlags = stdenv.lib.optional (!static) "--shared";
  
    preConfigure = ''
      if test -n "$crossConfig"; then
        export CC=$crossConfig-gcc
      fi
    '';
  
    postInstall = ''
      _moveToOutput lib/libz.a "$static"
    '';
  
    # As zlib takes part in the stdenv building, we don't want references
  
negative.code: 
  let version = "1.2.8"; in
  
  stdenv.mkDerivation rec {
    name = "zlib-${version}";
  
    src = fetchurl {
  