Hostname

echo $TARGET_HOSTNAME > $MOUNTPOINT/etc/hostname

Allow user in wheel group to use sudo

mv $MOUNTPOINT/etc/sudoers $MOUNTPOINT/etc/sudoers.original
tee $MOUNTPOINT/etc/sudoers << EOF
root ALL=(ALL) ALL
%wheel ALL=(ALL) ALL
@includedir /etc/sudoers.d
EOF

Set timezone

ln -sf /usr/share/zoneinfo/Etc/$TARGET_TIMEZONE $MOUNTPOINT/etc/localtime

Chroot into the new system