To build your changes using docker, you can use the following flow:

• in one window run make
• in another one run make ssh to have a shell into the container
  • don't forget to run ./scripts/setup-ocaml.sh to set up opam/ocaml/etc.
  • don't forget to run eval $(opam config env) as well
  • make build should work after that :)

If you need to re-build the container, after an important change like an OCaml version update, you can make rebuild.