anchor.diff:  
     # Allow the stdenv to determine fetchurl, to cater for strange
     # requirements.
  -  fetchurl = useFromStdenv (stdenv ? fetchurl) stdenv.fetchurl
  +  fetchurl = useFromStdenv "fetchurl"
       (import ../build-support/fetchurl {
         inherit stdenv curl;
       });
  
positive.code:   # inside the set for derivations.
    recurseIntoAttrs = attrs: attrs // {recurseForDerivations = true;};
  
    useFromStdenv = hasIt: it: alternative: if hasIt then it else alternative;
  
    lib = library;
  
  
negative.code:    * pkgconfig is optionally taken from the stdenv to allow bootstrapping
     * of glib and pkgconfig itself on MinGW.
     */
    pkgconfig = useFromStdenv "pkgconfig"
      (import ../development/tools/misc/pkgconfig {
        inherit fetchurl stdenv;
      });
  