Exported libraries are visible only to first-level dependent modules. And
to make them visible through several modules you need to export them in all
modules involved. For instance: there are 3 modules, mod1, mod2 and mod3.
mod3 depends on mod2, and mod2 depends on mod1. And mod1 exports the library,
libs. It is, naturally, visible in the mod2. But it is not visible for the
mod1. To make it visible for the mod3, you need to mark it as exported also
in the mod2.
But it is not visible for the mod1
But it is not visible for the mod3.