add "flasher flash_vbmeta" command
Flashes device vbmeta partition (which can be overriden with
deviceinfo_flash_fastboot_partition_vbmeta setting or --partition argument)
with custom vbmeta.img which has verity flag disabled,
so device can boot postmarketOS with no problems.
The process is described in Android_Verified_Boot_(AVB) wiki page in details. This is may be useful in general for all new devices with Android >= 8, that have Android Verified Boot enabled.
Small (2 Kb or 4 Kb, depending on deviceinfo_flash_pagesize) vbmeta.img is generated on the fly during this command and is removed after flashing.
Depends on avbtool merged first https://gitlab.com/postmarketOS/pmaports/-/merge_requests/1019
P.S. do not forget to update https://wiki.postmarketos.org/wiki/Deviceinfo_reference with new variable