postmarketOS/pmaports!700 adds a new "deviceinfo_bootimg_dtb_second"
option that places the DTB in the "second" area of the Android boot
image.
Attempt to detect this automatically by checking the extracted
second binary for the FDT magic (0xd00dfeed).
We are analyzing the `boot.img` with `file` before we send it to
`unpackbootimg`. File does not recognize all kinds of `boot.img` files,
which `unpackbootimg` can extract, so we need a way to skip this check.
Details:
* Add `-f` parameter, continues extraction with a warning if the file
seems to be invalid
* Tell the user that `-f` can be used if the `boot.img` is invalid and
it's not specified
* Consistent spelling of `boot.img` instead of `bootimg` in messages
Fixes#1608
Oliver Smith
lambdadroid
Oliver Smith
drebrez