anchor.diff:  
   let version = "1.2.8"; in
   
  -stdenv.mkDerivation rec {
  +stdenv.mkDerivation (rec {
     name = "zlib-${version}";
   
     src = fetchurl {
  
positive.code:   # As zlib takes part in the stdenv building, we don't want references
    # to the bootstrap-tools libgcc (as uses to happen on arm/mips)
    NIX_CFLAGS_COMPILE = stdenv.lib.optionalString (!stdenv.isDarwin) "-static-libgcc";
  
    postInstall = stdenv.lib.optionalString stdenv.isDarwin ''
      # 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
    '';
  
    crossAttrs = {
      dontStrip = static;
  
negative.code:     description = "Lossless data-compression library";
      license = licenses.zlib;
    };
  } // (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 {}))
  