Update shell.nix

Author: thomashoneyman

shell.nix

@@ -9,7 +9,7 @@ let
     repo = "easy-purescript-nix";
     rev = "7ff5a12af5750f94d0480059dba0ba6b82c6c452";
     sha256 = "0af25dqhs13ii4mx9jjkx2pww4ddbs741vb5gfc5ckxb084d69fq";
-  }) {};
+  }) { inherit pkgs; };
 
 in pkgs.stdenv.mkDerivation {
   name = "setup-purescript";