flake.nix: use flake-utils for system gen

flake.lock

@@ -1,5 +1,23 @@
 {
   "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1731533236,
+        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1771848320,
@@ -18,8 +36,24 @@
     },
     "root": {
       "inputs": {
+        "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs"
       }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
     }
   },
   "root": "root",

flake.nix

@@ -3,33 +3,37 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
   };
 
   outputs =
-    { self, nixpkgs }:
-    let
-      supportedSystems = [
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+    }:
+    flake-utils.lib.eachSystem
+      [
         "x86_64-linux"
         "aarch64-linux"
-      ];
-      forAllSystems = nixpkgs.lib.genAttrs supportedSystems;
-    in
-    {
-      nixosModules.default = import ./module.nix;
-      nixosModules.arr-init = import ./module.nix;
-
-      checks = forAllSystems (
+      ]
+      (
         system:
         let
           pkgs = nixpkgs.legacyPackages.${system};
         in
-        import ./tests {
-          inherit pkgs;
-          lib = nixpkgs.lib;
-          inherit self;
-        }
-      );
+        {
+          checks = import ./tests {
+            inherit pkgs;
+            lib = nixpkgs.lib;
+            inherit self;
+          };
 
-      formatter = forAllSystems (system: nixpkgs.legacyPackages.${system}.nixfmt-tree);
+          formatter = pkgs.nixfmt-tree;
+        }
+      )
+    // {
+      nixosModules.default = import ./module.nix;
+      nixosModules.arr-init = import ./module.nix;
     };
 }