chore(common): builder should make sure that dep builds are not later called as child builds and vice-versa

> Compare the later entries in both sections; they're nigh-identical.
>
> First set of calls: as a child script, from the top-level build.sh.
>
> Second set: as a _dependency_, from `web/src/test/manual`, which does not include `web/src/tools` as a viable child-project folder.

I reckon we should consider tweaking builder.inc.sh to handle the scenario of child vs dependency calls resulting in multiple calls.

_Originally posted by @mcdurdin in https://github.com/keymanapp/keyman/issues/9743#issuecomment-1757122400_