dune is a newer build system for ocaml that tries to unify the different build systems of ocaml by invocation of xkcd 927. Success is imminent, the majority of opam packages now use dune!
Advantages over oasis:
configure step and flags (but easy workaround)
This is in preparation for making the pgsolver dependency optional and therefore being able to merge the pgsolver branch to master. I hope that this will be easier with dune than with oasis.