Refine dependencies on dev-deps

Refine dependencies on dev-deps

Currently whenever a dev-dep is brought in to the build process the entire
library is rebuilt, but this is just unnecessary recompilation because the
library *can't* depend on the dev-dep.

This commit refines the dependency graph so the lib stage only depends on
transitive dependencies (non-dev-deps), and a new stage for tests was added
which depends on the packages libraries *and* the dev-deps. This way only the
test are rebuilt when dev-deps change, not libraries.