added overlay

flake.nix

@@ -12,7 +12,7 @@
   outputs =
     inputs:
     inputs.flake-parts.lib.mkFlake { inherit inputs; } {
-      imports = [ ];
+      imports = [ inputs.flake-parts.flakeModules.easyOverlay ];
 
       systems = builtins.attrNames inputs.nixpkgs.legacyPackages;
 
@@ -21,11 +21,14 @@
           config,
           system,
           pkgs,
-          self',
           ...
         }:
         {
-          packages.default = pkgs.stdenv.mkDerivation {
+          overlayAttrs = {
+            inherit (config.packages) nesrx;
+          };
+          packages.default = config.packages.nesrx;
+          packages.nesrx = pkgs.stdenv.mkDerivation {
             name = "nesrx";
             src = "${inputs.nesrx}";
             nativeBuildInputs = with pkgs; [ cmake ];