on post-fs
    mkdir /mnt/cust 0775 system system
    mount erofs loop@${MAGISKTMP}/cust.img /mnt/cust ro,seclabel
    wait /system
    mount overlay overlay /system_ext lowerdir=/mnt/cust/system_ext:/system_ext,seclabel
    mount overlay overlay /product lowerdir=/mnt/cust/product:/product,seclabel
    mount overlay overlay /system/priv-app lowerdir=/mnt/cust/system/priv-app:/system/priv-app,seclabel