It's a bit of a Catch-22. Work around it by making an app (or script) post for your app (or script), but put "(Placeholder)" in the title and tag it with placeholder.
Also, indicate in the post that the app is not yet ready for prime time.
This has already been done a few times, for example:
- "Chatdump - a site monitor (placeholder)"
- "A small Stack Overflow browser for Android, for a school project (Placeholder)"
Warning: Don't abuse this, though, or create an essentially empty post and not update it expeditiously. Otherwise the question will be closed and, if not corrected, quickly deleted.