I had the impression this fills the same role as bower, mpm (non global) dependency or plain custom vendor dirs handled with your favourite git module paraphernalia: your build is the place your dependencies live (+ possible cache directory somewhere else). And, these you use this packaging system to manage your build, not the deployment of your (iirc statically linked) build artifacts.

While technically the cache directory is a place where files can accumulate outside the view of a well documented and designed administrative tools, this is common problem shared with many tools including your favourite browser.