It looks like something changed in debhelper recently, and the package FTBFS. I fixed that by editing libgen-ocaml-dev.install.in (I pushed the fix).
Oh, I forgot to check: your package installs some .cmxs files. Please consider putting them (along with META and .cma files) in a separate libgen-ocaml package (unless you have a good reason not to do so). Also, please call dh_install with --fail-missing.