Context

This MR fixes the handling of private library and more generally private targets.

A Private library attached to an opam package should have a package stanza in its dune file.
When depending on an internal private target (not attached to an opam package), one must propagate the dependencies of the private target when computing opam deps.

Manually testing the MR

Document the interface of any function added or modified (see the coding guidelines)
Document any change to the user interface, including configuration parameters (see node configuration)
Provide automatic testing (see the testing guide).
For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
Select suitable reviewers using the Reviewers field below.
Select as Assignee the next person who should take action on that MR

Edited May 18, 2022 by Hugo Heuzard