anchor.diff:  
       nativeBuildInputs = [ perl pkgconfig ];
   
  -    buildInputs = [ curl openssl sqlite ] ++
  -      lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium;
  +    buildInputs = [ curl openssl sqlite xz ]
  +      ++ lib.optional (stdenv.isLinux || stdenv.isDarwin) libsodium;
   
       propagatedBuildInputs = [ boehmgc ];
   
  
positive.code: { lib, stdenv, fetchurl, perl, curl, bzip2, sqlite, openssl ? null
  , pkgconfig, boehmgc, perlPackages, libsodium
  , storeDir ? "/nix/store"
  , stateDir ? "/nix/var"
  
negative.code:    };
  
     nixUnstable = lib.lowPrio (common rec {
       name = "nix-1.11pre4334_7431932";
       src = fetchurl {
         url = "http://hydra.nixos.org/build/28747184/download/4/${name}.tar.xz";
         sha256 = "ccb0c5be03b9af1bf89e79758868b0cd62c79fd7a0f0791cdb99df86e4240fc4";
       };
     });
  
  