Code review comment for lp:~ltrager/maas-images/lp1702976

My comments from my original merge proposal still stand here:
  https://code.launchpad.net/~dannf/maas-images/lp1702976/+merge/327308

Specifically, I'd prefer we do this for arm*, just just for arm64, and that we include all the bus drivers, not just the i2c-thunderx driver. I don't know of any specific system that would be fixed by either of the above - but seems like a cleaner future-proofing. And obviously, it's ultimately your call.

I'd also like to continue to ask that we use 'dpkg --print-architecture' instead of 'uname -m'. From chatting on IRC, it sounds like qemu-user does emulate 'uname -m' to match the userspace, but that's just one form of a non-native build mechanism. Consider if we were building images for armhf on an arm64 host in an lxd container:

root@armhf:~# uname -m
armv8l

Whereas, we know in this case 'dpkg --print-architecture' will always report the thing we want to know:
root@armhf:~# dpkg --print-architecture
armhf