feat: add an overlay output

Signed-off-by: Raito Bezarius <masterancpp@gmail.com>

default.nix

@@ -1,5 +1,41 @@
 { sources ? import ./npins, pkgs ? import sources.nixpkgs {} }:
 {
+  overlay = self: super: 
+  let
+    inherit (super) lib;
+  in
+  {
+    ofborg = super.rustPlatform.buildRustPackage {
+      name = "ofborg";
+      src = super.nix-gitignore.gitignoreSource [ ] ./.;
+
+      nativeBuildInputs = with pkgs; [
+        pkg-config
+        rustPackages.clippy
+      ];
+
+      buildInputs = lib.optionals super.stdenv.isDarwin (with pkgs; [
+        darwin.apple_sdk.frameworks.Security
+        darwin.apple_sdk.frameworks.CoreFoundation
+      ]);
+
+      preBuild = ''
+        cargo clippy
+      '';
+
+      doCheck = false; # Tests require access to a /nix/ and a nix daemon
+      checkInputs = with super; [
+        lix
+      ];
+
+      cargoLock = {
+        lockFile = ./Cargo.lock;
+        outputHashes = {
+          "hubcaps-0.6.2" = "sha256-yyHOCxUsehvtYfttRY4T9TDrJhSKGpJRa/SX3Sd1TNc=";
+        };
+      };
+    };
+  };
   packages = {
     ofborg = pkgs.rustPlatform.buildRustPackage {
       name = "ofborg";