does anyone know whether dune/ocamlbuild go beyond the timestamp model of
dependency employed by make?
which would be looking at the signature digests of dependent modules and determining
whether to recompile according to change there.
and then beyond that there is the prospect of ruling out at a recompile of a client module on basis of a signature fragment it records (according to its usage of particular components) compared to the newly updated signature of the target module.