wic: Add partition type for msdos partition tables
In order to create a msdos partition table disk image that can auto
expand after the image is copied to an SD card, wic needs the ability
to have a primary partition as the last entry. The desired use case
is to be able to create an A/B update partition image scheme with a
/var volume that can be auto expanded to the remainder of the SD card
at run time.
The typical .wks file will look similar to the following:
With the patch applied a primary partition can be created at the end
of the image which can be expanded to fill the free space on the media
where the image has been copied, which looks like:
Disk boot.img: 890940s
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
