segfault instead of passphrase prompt

There seems to be a regression with mkinitfs 3.11.0_rc2, instead o passphrase prompt I get a segfault and am dropped into an emergency shell.

From the emergency shell I can cryptsetup open my root device just fine and zpool import -a and zfs mount -a, but when I exit the shell I get a busybox message and a reboot.

I use syslinux and have a separate /boot.

I managed to, from the emergency shell, do a zfs rollback to the latest snapshot of the rootfs dataset and restore the /boot to the same contents as the time of the snapshot, and then boot successfully.

I have now pinned mkinitfs=3.10.2-r1 (luckily I keep an apk cache), upgraded all other packages, successfully rebooted and confirmed that it is mkinitfs 3.11.0_rc2 that is the culprit.

@ncopa @sertonix