CD creation fails with "disk full", because of rounding errors.
The minimum size of data-allocation is a 'cluster', which is a
power-of-two multiple of sectors.
mkfs.msdos chooses minimum FAT and cluster size for image: FAT12<16G
mkfs.msdos uses block-count where a block is 1024 B, but must be rounded
up to track_size with 32 sectors.
Round up each file to clusters before summing.
A sub-directory entry needs 1 cluster minimum.
When we've got multiple copies of the same initramfs hard-linked
together, gzip gets unhappy when we start modifying things
later. Explicitly break the links to fix that.
Steve McIntyre
Philipp Hahn
Didier Raboud