Pinenote includes waveform lookup tables that are proprietary and only available through the `waveform` partition. Before, we packaged empty files for the firmware so that mkinitfa does not fail. The init scripts then extracts the waveform binaries on first boot. Unfortunately, this has the consequence that of overriding the extracted binaries every boot. Fixes this by only creating stub files when files are missing so mkinitfs does not fail via pre upgrade and install script. Part-of: <https://gitlab.postmarketos.org/postmarketOS/pmaports/-/merge_requests/8639>