985: Permit raspberry pi (and other architectures) builds r=mergify[bot] a=abondis
## What type of PR?
Enhancement
## What does this PR do?
Add an option to select base images and permit building for different CPU architectures.
### Related issue(s)
N/A
## Prerequistes
- [X] documentation updated accordingly
- [x] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.
Co-authored-by: Aurélien Bondis <aurelien.bondis@gmail.com>
Co-authored-by: Aurelien <aurelien.bondis@gmail.com>
Adam Ward