test that flutter_rust_bridge works

flutter_app/rust_builder/cargokit/build_tool/bin/build_tool.dart

@@ -0,0 +1,8 @@
+/// This is copied from Cargokit (which is the official way to use it currently)
+/// Details: https://fzyzcjy.github.io/flutter_rust_bridge/manual/integrate/builtin
+
+import 'package:build_tool/build_tool.dart' as build_tool;
+
+void main(List<String> arguments) {
+  build_tool.runMain(arguments);
+}