Install dev deps using opam install DIR (opam 2)
Install dev deps using opam install DIR (opam 2)

This has the advantage of respecting dependency version constraints. See

  https://github.com/ocaml/opam/issues/2750#issuecomment-331874265

c-cube/lwt,ocsigen/lwt,ocsigen/lwt,c-cube/lwt,c-cube/lwt,ocsigen/lwt