Add systems input to leverage extensible flake systems pattern

Add the systems input to transitively leverage the "externally
extensible flake systems" [1] pattern.

[1]: https://github.com/nix-systems/nix-systems

Author: trueNAHO

flake.lock

@@ -8,7 +8,13 @@
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
-    utils.url = "github:numtide/flake-utils";
+    systems.url = "github:nix-systems/default";
+
+    utils = {
+      url = "github:numtide/flake-utils";
+      inputs.systems.follows = "systems";
+    };
+
     flake-compat = {
       url = "github:edolstra/flake-compat";
       flake = false;

flake.nix

@@ -50,11 +50,11 @@ let
     flakeInputs = ''
       deploy-rs.url = "${../..}";
       deploy-rs.inputs.utils.follows = "utils";
+      deploy-rs.inputs.systems.follows = "systems";
       deploy-rs.inputs.flake-compat.follows = "flake-compat";
 
       nixpkgs.url = "${inputs.nixpkgs}";
       utils.url = "${inputs.utils}";
-      utils.inputs.systems.follows = "systems";
       systems.url = "${inputs.utils.inputs.systems}";
       flake-compat.url = "${inputs.flake-compat}";
       flake-compat.flake = false;