Fixed env for flake

flake.nix

@@ -49,8 +49,11 @@
           ];
           # For rust-analyzer
           RUST_SRC_PATH = "${pkgs.rust.packages.stable.rustPlatform.rustLibSrc}";
+
+          # Amethyst codename
+          AMETHYST_CODENAME = "Nixilicious";
         };
 
         formatter = pkgs.alejandra;
       });
-}
+}