allow building images for multiple distros
- changing the distro or mirror can be done either via environment variable or via CLI option
 - allow generating images for only a selected number of platforms via CLI arguments
 - the default behaviour (no options) is unchanged
 - update to u-boot 2023-10-10 and 2023-10-18
 - firedecor is named reform-firedecor in unstable
 - reform-tools 1.33
 
Edited  by Johannes Schauer Marin Rodrigues