Add `cut` binary to the initramfs

Add `cut` binary to the initramfs

Since the `cut -b` command is used by `parse-zfs.sh`,
ensure that it is copied to the initramfs.

Fix spl_hostid when set by cmdline. This follows a
similar logic from the `zgenhostid` script, using `echo`
instead of `printf`.

Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ben Cordero <bencord0@condi.me>
Closes #8197