anchor.diff:    outputs = [ "dev" "out" "static" "man" ];
     setOutputFlags = false;
   
  -  configureFlags = stdenv.lib.optional (!static) "--shared";
  -
     preConfigure = ''
       if test -n "$crossConfig"; then
         export CC=$crossConfig-gcc
       fi
     '';
   
  +  configureFlags = stdenv.lib.optional (!static) "--shared";
  +
     postInstall = ''
       _moveToOutput lib/libz.a "$static"
  +  ''
  +    # 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.
  +  + stdenv.lib.optionalString stdenv.isDarwin ''
  +    for file in $out/lib/*.so* $out/lib/*.dylib* ; do
  +      install_name_tool -id "$file" $file
  +    done
     '';
   
     # As zlib takes part in the stdenv building, we don't want references
  
positive.code: 
  let version = "1.2.8"; in
  
  stdenv.mkDerivation (rec {
    name = "zlib-${version}";
  
    src = fetchurl {
  
negative.code:     license = licenses.zlib;
      platforms = platforms.all;
    };
  }
  
  