Building for Ubuntu 16.04 LTS in CI

I still like my VMs for this. Its right here and I can log into it and try things…

I based my apt-gets on your ci/ubuntu-18.04/Dockerfile and encountered three issues:

  1. guile is unavailable
  2. libargon2-0-dev is unavailable (used by php - probably explains later php problems)
  3. libltdl-dev is needed and available, but wasn’t in your 18.04 Dockerfile.

I built graphviz from a fresh git clone using:
./autogen.sh
./configure --disable-ocaml --disable-php
make

Builds with ocaml or php enabled failed, probably not so important why right now. I think we should just build ubuntu-16.04 packages without ocaml and php. The ./configure is in debian/rules, so somehow these rules should be modified for different versions of Ubuntu. I’m not a Debian expert, so not sure how to do that?