Add packages to flake.nix

flake.nix

@@ -1,5 +1,19 @@
 {
-  outputs = {...}: {
+  inputs = {
+    nixpkgs.url = "nixpkgs";
+  };
+
+  outputs = { self, nixpkgs, ...}:
+  let
+    pkgs = import nixpkgs {
+      # For now we only support x86
+      system = "x86_64-linux";
+      overlays = [ self.overlays.default ];
+    };
+  in
+    {
       bscOverlay = import ./overlay.nix;
+      overlays.default = self.bscOverlay;
+      packages.x86_64-linux = pkgs;
     };
 }