anchor.diff:  { name ? "", stdenv, nativeTools, nativeLibc, nativePrefix ? ""
   , cc ? null, libc ? null, binutils ? null, coreutils ? null, shell ? stdenv.shell
   , zlib ? null, extraPackages ? [], extraBuildCommands ? ""
  -, dyld ? null # TODO: should this be a setup-hook on dyld?
   , isGNU ? false, isClang ? cc.isClang or false, gnugrep ? null
   }:
   
  
positive.code:       }
      ''
  
      + optionalString (!nativeLibc) (if (!stdenv.isDarwin) then ''
        dynamicLinker="$libc/lib/$dynamicLinker"
        echo $dynamicLinker > $out/nix-support/dynamic-linker
  
  
negative.code:       # explicit overrides of the dynamic linker by callers to gcc/ld
        # (the *last* value counts, so ours should come first).
        echo "-dynamic-linker" $dynamicLinker > $out/nix-support/libc-ldflags-before
      '')
  
      + optionalString (!nativeLibc) ''
  