nix: use rustoverlay; thanks nullcube <3

flake.lock

@@ -18,7 +18,28 @@
     },
     "root": {
       "inputs": {
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "rust-overlay": "rust-overlay"
+      }
+    },
+    "rust-overlay": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1722305989,
+        "narHash": "sha256-ljiuTGSFuEtudqFqp/5Wr1OuEsVCjur/F2CmlNujSjc=",
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "rev": "38c2f156fca1868c8be7195ddac150522752f6ab",
+        "type": "github"
+      },
+      "original": {
+        "owner": "oxalica",
+        "repo": "rust-overlay",
+        "type": "github"
       }
     }
   },

flake.nix

@@ -3,9 +3,27 @@
 
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs?ref=nixos-unstable";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
-  outputs = { self, nixpkgs }: {
-    devShells.x86_64-linux.default = import ./shell.nix { pkgs = nixpkgs.legacyPackages.x86_64-linux; };
-  };
+  outputs = { nixpkgs, rust-overlay, ... }:
+    let
+      # System types to support.
+      supportedSystems = [
+        "x86_64-linux"
+        "aarch64-linux"
+      ];
+
+      forAllSystems = function: nixpkgs.lib.genAttrs supportedSystems
+        (system: function (import nixpkgs {
+          inherit system;
+          overlays = [ rust-overlay.overlays.default ];
+        }));
+    in
+    {
+      devShells = forAllSystems (pkgs: { default = import ./shell.nix { inherit pkgs; }; });
+    };
 }