chore(common): add new test for child of dependency for builder

For the `debug-deps` test, it would be nice to have an action that verifies that a child action is skipped if it was already run due to dependency mode.

So, a setup like...

parent:
```sh
builder_describe "foo" \
"@/resources/build/test/debug-deps/dep/child" \
"@/resources/build/test/debug-deps/dep"
```

Of course, a more likely case is where the first 'dependency' there is triggered by a different dependency that happens to depend on `dep/child`.

_Originally posted by @jahorton in https://github.com/keymanapp/keyman/pull/11410#pullrequestreview-2047342095_