<rant>:
If a package is needed to perform the validation tests you setup for the building of your app (and without that package the build will simply fail), then please EXPLICITLY list that package in the documentation/README/Build instructions of your app.
</rant>
@joao ...or better: don't specify the dependencies in the README itself at all. Rather have a link in there that points to a *tested* list of dependencies (e.g. to the deps installed during gitlab-ci). That makes sure that those build dependencies are tested on commit (and hence must be updated when code changes need new dependencies).
#phosh e.g. does this at https://gitlab.gnome.org/World/Phosh/phosh#dependencies