nix fmt; add aarch64 arch to flake

flake.nix

@@ -3,7 +3,6 @@
 # either `curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install`
 # or https://github.com/DeterminateSystems/nix-installer
 # and then `nix build` or `nix develop`
-
 {
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
@@ -16,12 +15,18 @@
 
   outputs = inputs:
     inputs.flake-parts.lib.mkFlake {inherit inputs;} {
-      systems = [ "x86_64-linux" ];
+      systems = ["x86_64-linux" "aarch64-linux"];
       imports = [
         inputs.treefmt-nix.flakeModule
       ];
-      perSystem = { config, self', pkgs, lib, system, ... }:
+      perSystem = {
-        let
+        config,
+        self',
+        pkgs,
+        lib,
+        system,
+        ...
+      }: let
         cargoToml = builtins.fromTOML (builtins.readFile ./Cargo.toml);
         nonRustDeps = [
           pkgs.libiconv
@@ -32,8 +37,7 @@
           name = "rust-toolchain";
           paths = [pkgs.rustc pkgs.cargo pkgs.cargo-watch pkgs.rust-analyzer pkgs.rustPlatform.rustcSrc];
         };
-        in
+      in {
-        {
         # Rust package
         packages.default = pkgs.rustPlatform.buildRustPackage {
           inherit (cargoToml.package) name version;