anchor.diff:  
   # Version dependent args
   , version, src, patches ? [], postPatch ? "", nativeBuildInputs ? []
  -, ...}@args:
  +, ...}:
   
   assert guileBindings -> guile != null;
  -
  -stdenv.mkDerivation rec {
  +let
  +  # XXX: Gnulib's `test-select' fails on FreeBSD:
  +  # http://hydra.nixos.org/build/2962084/nixlog/1/raw .
  +  doCheck = (!stdenv.isFreeBSD && !stdenv.isDarwin);
  +in
  +stdenv.mkDerivation {
     name = "gnutls-${version}";
   
     inherit src patches;
  
positive.code:   # for the actual fix.
    enableParallelBuilding = !guileBindings;
  
    buildInputs = [ lzo lzip nettle libtasn1 libidn p11_kit zlib gmp autogen ]
      ++ lib.optional doCheck nettools
      ++ lib.optional (stdenv.isFreeBSD || stdenv.isDarwin) libiconv
      ++ lib.optional (tpmSupport && stdenv.isLinux) trousers
      ++ [ unbound ]
      ++ lib.optional guileBindings guile;
  
    nativeBuildInputs = [ perl pkgconfig ] ++ args.nativeBuildInputs;
  
    # XXX: Gnulib's `test-select' fails on FreeBSD:
    # http://hydra.nixos.org/build/2962084/nixlog/1/raw .
    doCheck = (!stdenv.isFreeBSD && !stdenv.isDarwin);
  
    # Fixup broken libtool and pkgconfig files
    preFixup = lib.optionalString (!stdenv.isDarwin) ''
  
negative.code:   postPatch = ''
      sed '2iecho "name constraints tests skipped due to datefudge problems"\nexit 0' \
        -i tests/cert-tests/name-constraints
    '' + postPatch;
  
    preConfigure = "patchShebangs .";
    configureFlags =
  