I've had good experiences with travis recently, using the docker script
(an example here:
https://github.com/c-cube/iter/blob/master/.travis.yml).

if your package is opam 2-friendly it's just a matter of a local pin
and a few switches. there are other options (variables, really) to
install extra deps or deal with optional deps.

It's not particularly overkill since it just starts with a docker image
with pre-installed opam switches.

-- 
Simon Cruanes