Installer: warning about `avb_custom_key`
When installing (manual or graphical) to devices that support bootloader relocking, this message appears:
```
Erasing 'avb_custom_key' OKAY \[ 0.013s\]
Finished. Total time: 0.023s
Warning: skip copying avb_custom_key image avb footer (avb_custom_key partition size: 0, avb_custom_key image size: 1032).
```
This has caused some user concern as they feel it may not be possible to later lock their device without risking bricking it. @vincent notes this:
> Yes this is normal output. Probably because the avb_custom_key partition does not have an avb footer
Could we suppress this warning to alleviate concern?
issue