flake: allow overriding flake-parts systems

flake.lock

@@ -66,7 +66,23 @@
       "inputs": {
         "flake-compat": "flake-compat",
         "flake-parts": "flake-parts",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "systems": "systems"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1689347949,
+        "narHash": "sha256-12tWmuL2zgBgZkdoB6qXZsgJEH9LR3oUgpaQq2RbI80=",
+        "owner": "nix-systems",
+        "repo": "default-linux",
+        "rev": "31732fcf5e8fea42e59c2488ad31a0e651500f68",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default-linux",
+        "type": "github"
       }
     }
   },

flake.nix

@@ -4,6 +4,7 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
     flake-parts.url = "github:hercules-ci/flake-parts";
+    systems.url = "github:nix-systems/default-linux";
 
     flake-compat = {
       url = "github:edolstra/flake-compat";
@@ -12,15 +13,15 @@
   };
 
   outputs = {
+    self,
     nixpkgs,
     flake-parts,
-    self,
     ...
   } @ inputs: let
     pins = import ./npins;
   in
     flake-parts.lib.mkFlake {inherit inputs self;} {
-      systems = ["x86_64-linux" "aarch64-linux"];
+      systems = import inputs.systems;
       imports = [flake-parts.flakeModules.easyOverlay];
 
       perSystem = {
@@ -43,8 +44,13 @@
           directory = ./pkgs;
         };
 
-        formatter = pkgs.alejandra;
-        devShells.default = with pkgs; mkShell {buildInputs = [npins];};
+        formatter = config.packages.alejandra-custom;
+        devShells = {
+          default = self.devShells.${system}.npins;
+          npins = pkgs.mkShellNoCC {
+            packages = [pkgs.npins];
+          };
+        };
       };
     };
 }