Summary:
Using the same trick as for the java frontend: define a dune library
that takes either all the modules in the directory (except possibly
stubs) or none of the modules (except possible stubs).
In order to break the circular dependency between al/ and clang/,
introduce a dirty callback in clang/.
Reviewed By: dulmarod
Differential Revision: D21440823
fbshipit-source-id: ac6b40b4e