flake: clean of Rust installation

flake.nix

@@ -2,10 +2,6 @@
   description = "Rust development environment for oxitoko using fenix";
 
   inputs = {
-    fenix = {
-      url = "github:nix-community/fenix";
-      inputs.nixpkgs.follows = "nixpkgs-unstable";
-    };
     utils.url = "github:numtide/flake-utils";
     nixpkgs-unstable.url = "github:nixos/nixpkgs/nixos-unstable";
   };
@@ -14,26 +10,19 @@
     self,
     nixpkgs-unstable,
     utils,
-    fenix,
     ...
   }:
     utils.lib.eachDefaultSystem
     (
       system: let
-        pkgs = import nixpkgs-unstable {
-          inherit system;
-          overlays = [fenix.overlays.default];
-        };
+        pkgs = import nixpkgs-unstable { inherit system; };
         toolchain = pkgs.fenix.complete;
         dependencies = with pkgs; [ SDL2 SDL2_image ];
       in rec
       {
         # Executed by `nix build`
         packages.default =
-          (pkgs.makeRustPlatform {
-            inherit (toolchain) cargo rustc;
-          })
-          .buildRustPackage {
+          (pkgs.makeRustPlatform.buildRustPackage {
             pname = "rustboyadvance-ng";
             name = "rustboyadvance-ng";
             src = ./.;
@@ -51,14 +40,7 @@
         apps.default = utils.lib.mkApp {drv = packages.default;};
 
         # Used by `nix develop`
-        devShells.default = pkgs.mkShell rec {
-          buildInputs = with pkgs; [
-            (with toolchain; [
-              cargo rustc rust-src clippy rustfmt # rust components
-            ])
-          ] ++ dependencies;
-          RUST_SRC_PATH = "${toolchain.rust-src}/lib/rustlib/src/rust/library";
-        };
+        devShells.default = pkgs.mkShell rec { buildInputs = dependencies; };
       }
     );
 }