anchor.diff:        envVars = mkOption {
           internal = true;
           default = "";
  -        type = with pkgs.lib.types; string;
  +        type = types.string;
           description = "
             Environment variables used by Nix.
           ";
  
positive.code:         export ftp_proxy=${config.nix.proxy}
        '';
  
      users.extraUsers = map makeNixBuildUser (pkgs.lib.range 1 config.nix.nrBuildUsers);
  
      system.activationScripts.nix = stringAfter [ "etc" "users" ]
        ''
  
negative.code:               # in `build-chroot-dirs' - otherwise any builder that uses
                # /bin/sh won't work.
                binshDeps = pkgs.writeReferencesToFile config.system.build.binsh;
              in
                pkgs.runCommand "nix.conf" {extraOptions = config.nix.extraOptions; } ''
                  extraPaths=$(for i in $(cat ${binshDeps}); do if test -d $i; then echo $i; fi; done)
                  cat > $out <<END
                  # WARNING: this file is generated.
                  build-users-group = nixbld
  