add builttools as an option

modules/buildtools.nix

@@ -0,0 +1,40 @@
+{
+  pkgs,
+  lib,
+  config,
+  ...
+}: let
+  cfg = config.my.buildtools;
+in {
+  options.my.buildtools = {
+    native = lib.mkEnableOption "include native build tools";
+    dotnet = lib.mkEnableOption "include dotnet build tools";
+    rust = lib.mkEnableOption "include rust build tools";
+  };
+
+  config = lib.mkMerge [
+    (lib.mkIf cfg.native
+      {
+        environment.systemPackages = with pkgs; [
+          cmake
+          gnumake
+          gcc
+          gdb
+        ];
+      })
+    (lib.mkIf cfg.dotnet {
+      environment.systemPackages = with pkgs; [
+        dotnet-sdk_8
+      ];
+    })
+    (lib.mkIf cfg.rust {
+      environment.systemPackages = with pkgs; [
+        cargo
+        rustc
+        rustfmt
+        clippy
+        cargo-generate
+      ];
+    })
+  ];
+}