If mksquashfs is unavailable then set NO_SQUASHFS true so that a valid
OTA package is created.
Reduces the amount of output by (optionally) using quite zip/unzip
Make better use of sed (we don't need grep|sed as sed can match input).
Something isn't setting the path correctly when running in a 32-bit
chroot environment in ArchLinux. This causes the script to cd into
$WORK/xbin. The PATH incorrectly contains ".", so all attempted
commands (rm, mv, cp) fail to execute as it is trying to execute
$WORK/xbin/{rm, mv, cp}.
