bugfix: make sure busybox's fdisk output parsing is not positional, support qemu and fix debug output

[tlaurion]

This is mitigation for #1883

[JonathonHall-Purism]

IIRC, this will break on a device directly formatted FAT32 without being partitioned. (That's what I wrote above - in that case, fdisk prints out a partition table but with no partitions. The FAT32 "volume boot record" is essentially the same as a master boot record.)

Instead I'd suggest looking for the heading, then checking if there are any partition lines following it. awk would be a good fit for this.

If you don't beat me to it, I can suggest a solution here after I get through my post-holidays inbox 😁

[tlaurion]

I couldn't replicate under qemu with resized disk (mbr though)

https://matrix.to/#/!pAlHOfxQNPXOgFGTmo:matrix.org/$SjUpbwplho4wCQWscmHZUjX1tYTqYpoc7OMfkCqMLrs?via=matrix.org&via=nitro.chat&via=envs.net

# fdisk -l
fdisk: device has more than 2^32 sectors, can't use all of them
Disk /dev/vda: 2048 GB, 2199023255040 bytes, 4294967295 sectors
8421504 cylinders, 255 heads, 2 sectors/track
Units: sectors of 1 * 512 = 512 bytes

Device  Boot StartCHS    EndCHS        StartLBA     EndLBA    Sectors  Size Id Type
/dev/vda1 *  4,4,1       1023,254,2        2048    1953791    1951744  953M 83 Linux
/dev/vda2    1023,254,2  1023,254,2    39944190   41940991    1996802  975M  5 Extended
/dev/vda3    1023,254,2  1023,254,2     1953792   39942143   37988352 18.1G 83 Linux
/dev/vda5    1023,254,2  1023,254,2    39944192   41940991    1996800  975M 82 Linux swap

Partition table entries are not in disk order
~ # echo $?
0

Marking this PR as draft.