ReaR/PPC64: Cannot create DVD images including backup and cannot split DVD images

Issue

• On PPC64 and PPC64le, configuring ReaR to include the backup in the ISO image doesn't include the backup

  # cat /etc/rear/site.conf
  OUTPUT=ISO
  OUTPUT_URL=file:///home/backup/
  BACKUP=NETFS
  BACKUP_URL=iso:///OS
  BACKUP_PROG_EXCLUDE=( "${BACKUP_PROG_EXCLUDE[@]}" /home )
  # rear mkbackup
  
  # isoinfo -i /home/backup/my-system/rear-my-system.iso -l
  Directory listing of /
  d---------   0    0    0            2048 Apr 24 2018 [     28 02]  . 
  d---------   0    0    0            2048 Apr 24 2018 [     28 02]  .. 
  d---------   0    0    0            2048 Apr 24 2018 [     29 02]  boot 
  ----------   0    0    0        58123168 Apr 24 2018 [     37 00]  initrd.cgz 
  ----------   0    0    0        19793184 Mar 21 2018 [  28418 00]  kernel 
  d---------   0    0    0            2048 Apr 24 2018 [     31 02]  ppc 
  ...    
  

• On PPC64 and PPC64le, configuring ReaR to split the ISO image doesn't split the ISO image

  # cat /etc/rear/site.conf
  OUTPUT=ISO
  OUTPUT_URL=file:///home/backup/
  BACKUP=NETFS
  BACKUP_URL=iso:///OS
  BACKUP_PROG_EXCLUDE=( "${BACKUP_PROG_EXCLUDE[@]}" /home )
  ISO_MAX_SIZE=600
  
  # rear mkbackup
  
  # ls -1 /home/backup/my-system/*.iso
  /home/backup/my-system/my-system.iso