sysupgrade broken on imx nand targets (and maybe others too)

[Koen Vandeputte]

Hi Rodrigo,

After a long absence and now testing the latest master, I noticed that
imx nand flash sysupgrade was broken:

expected behaviour:
- scan the nand
- write image
- format empty space
-reboot

Seen behaviour:
- Scan the nand
- reboots

I traced it back to this batch of commits by you:

9d1e687da3 base-files: verify nand sysupgrade images
9710712120 base-files: accept gzipped nand sysupgrade images
af34733593 base-files: fix ubinized nand sysupgrade
e25e6d8e54 base-files: fix and clean up nand sysupgrade code


It can be easily confirmed by reverting /lib/upgrade/nand.sh with a
version before these commits are applied to it.

I added a "set -x" to nand.sh to get more detailed logs:
https://pastebin.com/raw/yxY0SK1x

Any idea?

Thanks,

Koen