[$] Protecting files with fs-verity

The developers of the Android system have, among their many goals, the wishto better protect Android devices against persistent compromise. It is badif a device is taken over by an attacker; it's worse if it remainscompromised even after a reboot. Numerous mechanisms for ensuring theintegrity of installed system files have been proposed and implementedover the years. But it seems there is always room for one more; to fillthat space, the fs-veritymechanism is being proposed as a way to protect individual files frommalicious modification.