anchor.diff:    ] ++ optionals stdenv.isCrossWin [
       "target-os=windows"
       "threadapi=win32"
  +    "binary-format=pe"
  +    "address-model=${if stdenv.isCross64 then "64" else "32"}"
  +    "architecture=x86"
     ];
     crossB2Args = concatStringsSep " " (genericB2Flags ++ crossB2Flags);
   
  
positive.code:     buildPhase = builder crossB2Args;
      installPhase = installer crossB2Args;
      postFixup = fixup;
    };
  }
  
negative.code: { stdenv, fetchurl, icu, expat, zlib, bzip2, python, fixDarwinDylibNames
  , toolset ? if stdenv.cc.isClang then "clang" else null
  , enableRelease ? true
  , enableDebug ? false
  