Specify the systems through a flake input.

flake.lock

@@ -35,7 +35,9 @@
         "nixpkgs": [
           "nixpkgs"
         ],
-        "systems": "systems"
+        "systems": [
+          "systems"
+        ]
       },
       "locked": {
         "lastModified": 1683635384,
@@ -69,7 +71,9 @@
     },
     "flake-utils": {
       "inputs": {
-        "systems": "systems_2"
+        "systems": [
+          "systems"
+        ]
       },
       "locked": {
         "lastModified": 1681202837,
@@ -172,6 +176,7 @@
         "nixpkgs": "nixpkgs",
         "pre-commit-hooks": "pre-commit-hooks",
         "rust-overlay": "rust-overlay",
+        "systems": "systems",
         "treefmt-nix": "treefmt-nix"
       }
     },
@@ -199,33 +204,16 @@
       }
     },
     "systems": {
+      "flake": false,
       "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
+        "lastModified": 1,
+        "narHash": "sha256-8wkkYGr1dPSnX9oVMX8D6dTOROXKOYpBTKfriA0sEBI=",
+        "path": "./systems.nix",
+        "type": "path"
       },
       "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
-      }
-    },
-    "systems_2": {
-      "locked": {
-        "lastModified": 1681028828,
-        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
-        "owner": "nix-systems",
-        "repo": "default",
-        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nix-systems",
-        "repo": "default",
-        "type": "github"
+        "path": "./systems.nix",
+        "type": "path"
       }
     },
     "treefmt-nix": {

flake.nix

@@ -1,11 +1,19 @@
 {
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
-    flake-utils.url = "github:numtide/flake-utils";
+    systems = {
+      url = "path:./systems.nix";
+      flake = false;
+    };
+    flake-utils = {
+      url = "github:numtide/flake-utils";
+      inputs.systems.follows = "systems";
+    };
     devshell = {
       url = "github:numtide/devshell";
       inputs = {
         nixpkgs.follows = "nixpkgs";
+        systems.follows = "systems";
       };
     };
     pre-commit-hooks = {
@@ -46,7 +54,7 @@
     , devshell
     , treefmt-nix
     , pre-commit-hooks
-    ,
+    , ...
     }:
     {
       lib = import ./nix/lib.nix {
@@ -60,11 +68,7 @@
       };
     }
     //
-    (flake-utils.lib.eachSystem
-      [
-        flake-utils.lib.system.x86_64-linux
-        flake-utils.lib.system.aarch64-linux
-      ]
+    (flake-utils.lib.eachDefaultSystem
       (system:
       let
         pkgs = import nixpkgs {

systems.nix

@@ -0,0 +1,4 @@
+[
+  "x86_64-linux"
+  "aarch64-linux"
+]