Avoid rebuilding local dependency if it has already been built on its own

I have a local dependency in my stack.yaml:

extra-deps:
    - foo/bar
    - foo/quux

I also have a stack.yaml in foo:

packages:
    - bar
    - quux

Now let's suppose I do the following sequence of actions:

1. Change something in foo/bar or foo/quux
2. Do a stack build in foo
3. Do a stack build in the root directory

If #2 succeeds, I would expect #3 to not rebuild foo/bar or foo/quux, since step #2 already did that. However, it seems the build under foo is not reused for the build in / by default. Is there a way to do that?