We don't restrict LIBDEPS usage much, but we probably should. At least the following should probably be disallowed:

• We should only allow one of LIBDEPS or LIBDEPS_PRIVATE on anything that is a Program. Since things don't link to Program nodes, it doesn't matter which, but there is no advantage to declaring them one way or the other. Since LIBDEPS_PRIVATE doesn't really mean anything (or LIBDEPS_INTERFACE for that matter), we should disallow use of all forms other than LIBDEPS on things that are {{Program}}s.

• We have a facility for injecting reverse dependency edges via [PROG|LIB]DEPS_DEPENDENTS. An injectable library by definition adds behavior that may or may not be present. We should disallow linking directly to nodes that use DEPS_DEPENDENTS, since if that happens the node participates in both the forward and reverse sense, which is very confusing.

• Continuing with DEPS_DEPENDENTS, with the above rule enforced, it doesn't make sense for any Library that declares itself to function via reverse dependency edges to have anything other than LIBDEPS_PRIVATE dependencies, since if the injectable library is truly optional, it cannot be the source of any resolved symbols.

• If it is not currently enforced, we should ensure that for a given Program or Library, that any other library is listed exactly once among its LIBDEPS, LIBDEPS_PRIVATE, and LIBDEPS_INTERFACE sections.

While working on the above, we should also investigate any use of DEPS_DEPENDENTS in the community repo, as it is somewhat unclear what purpose they serve.