[FIX] Osmosis fix too many --m flags

[hdevine825]

This PR…

• Solves an issue where Osmosis fails due to a merge command after only one input.

Considerations and implementations

Uses tracking of count of land tile files to exclude the --m flag after the first file.

How to test

1. ...
2. ...

Pull Request Checklist

• [x] Reviewed the Contributing Guidelines
  • Especially the Pull-Requests section
• [x] Commits (and commit-messages) are understandable
• [x] Tested with macOS / Linux
• [ ] Tested with Windows