How to pass arguments to dependent tasks?

See this `serve` task as an example, https://github.com/dart-lang/dart-pad/blob/b9a426f73c1b4dff267b7328d3c6fac964b560bd/tool/grind.dart#L28.

This depends on the `build` task, which accepts a `--debug` flag.

I want to run the `serve` task, with `--debug` set for the nested `build` task, but I can't figure out how to do it?

I tried `grind serve build --debug`, `grind serve --debug`, `grind serve --debug build --debug`, but none of those options work, they all ultimately end up with an error like this:

```
Unhandled exception:
GrinderException: Cannot run a task multiple times with different arguments
#0 Grinder._postOrder (package:grinder/src/grinder.dart:88:9)
#1 Grinder._postOrder (package:grinder/src/grinder.dart:78:7)
#2 Grinder.start (package:grinder/src/grinder.dart:168:7)
#3 runTasks (package:grinder/src/cli.dart:69:38)
#4 grind (package:grinder/grinder.dart:45:12)
#5 main (/dart-pad/tool/grind.dart:21:28)
#6 _delayEntrypointInvocation. (dart:isolate-patch/isolate_patch.dart:295:32)
#7 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)
```

I did some debugging and it looks like the task is trying to run both with empty arguments and with `["--debug"]`. So I think the dependency set up by `serve` is implicitly trying to run it with no arguments, or something like that?