anchor.diff:    callPackage = newScope gnu;
   
     gnu = {
  -    hurdCross = forceBuildDrv(import ./hurd {
  +    hurdCross = forceBuildDrv(callPackage ./hurd {
         inherit fetchgit stdenv autoconf libtool texinfo
           glibcCross hurdPartedCross;
         inherit (gnu) machHeaders mig;
  
positive.code:       gccCross = gccCrossStageFinal;
      });
  
      hurdCrossIntermediate = forceBuildDrv(import ./hurd {
        inherit fetchgit stdenv autoconf libtool texinfo glibcCross;
        inherit (gnu) machHeaders mig;
        automake = automake111x;
        headersOnly = false;
        cross = assert crossSystem != null; crossSystem;
  
negative.code:       hurd = null;
      };
  
      libpthreadCross = forceBuildDrv(callPackage ./libpthread {
        inherit fetchgit stdenv autoconf automake libtool glibcCross;
        inherit (gnu) machHeaders hurdHeaders;
        hurd = gnu.hurdCrossIntermediate;
  