Fix squisher on ArchLinux 32-bit chroot.

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}.