Fix bootstrap to account for mli deps
Fix bootstrap to account for mli deps

Previously, it would ignore interface deps but that is obviously wrong.
It should use botha intf and impl files to discover deps.

Signed-off-by: Rudi Grinberg <4c46c202a3b8207ad5740134b125aae40c6c67a8@gmail.com>

janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,dra27/jbuilder