* Replace bundled debian/dh-cargo-built-using with the one from e.g. dh-cargo.

* Automate Recommends: Waypipe dynamically loads some libraries at runtime
  instead of linking with them. We want to treat these as optional, placing them
  in Recommends. Currently, the list is very crudely populated based on
  inspecting Waypipe's dynamic loading of shared objects. No symbol version
  tracking is performed, while ideally we'd want to do the job that
  dpkg-shlibdeps does for linked libraries.

* Disable build-time tests when cross-building.

* Specify features in Rust build-deps.
