Root path might not be needed for vfat with file list

[detly]

If I have this config:

image usb.img {
    hdimage {
        partition-table-type = gpt
    }
    partition root {
        image = "root.img"
    }
}

image root.img {
    size = "64M"
    vfat {
        files = {
            "readme.md"
        }
    }
}

...then I need to invoke genimage with a valid --rootpath. I'm not sure why though, because (I think) all the necessary files are specified, and could just be copied straight to tmppath as per other filesystems discussed in #181.

If I use empty = true (as a child key of root.img) then indeed I can skip supplying or creating rootpath. This suggests to me that vfat partitions populated from a list of files could also qualify for not needing a rootpath.

• genimage: 16
• OS: Ubuntu 23.10