The opam CloudI 2.0.0 package was added, though you will need CloudI installed too:
Download 2.0.0 from https://osdn.net/dl/cloudi/cloudi-2.0.0.tar.gz
Using the configure flag --enable-ocaml-support provides what the opam package provides in the path where CloudI is installed. CloudI can help you make source code fault-tolerant and scale in a variety of programming languages (C/C++, Erlang/Elixir, Go, Haskell, Java, JavaScript, OCaml, Perl, PHP, Python and Ruby).
For more information: