anchor.diff:    nixVersion = getVersion nix;
   
     isNix20 = versionAtLeast nixVersion "2.0pre";
  +  isNix23 = versionAtLeast nixVersion "2.3pre";
   
     makeNixBuildUser = nr:
       { name = "nixbld${toString nr}";
  
positive.code:             '' else ''
                echo "Checking that Nix can read nix.conf..."
                ln -s $out ./nix.conf
                NIX_CONF_DIR=$PWD ${cfg.package}/bin/nix show-config >/dev/null
              '')
        );
  
  
negative.code:           builders =
          ''}
          system-features = ${toString cfg.systemFeatures}
          ${optionalString isNix23 ''
            sandbox-fallback = false
          ''}
          $extraOptions
  