Those scripts could only be run once, because mount errors out
if it tries to mount an already mounted fs (or unmount a non
mounted fs). This changes generation of the scripts so that
any mount is preceded with "mountpoint -q || ", and any umount
is preceded with "mountpoint -q && ".
The command for unmounting the kernel vfs is now
umount -Rv $LFS
So we have first to use that command in teardown (change in
kernfs.xsl). Second, since the command tries to umount
$LFS, but the Makefile is on $LFS, it fails. Ignore the
error in the Makefile (change in master.sh)