Raspberry Pi 5 support?

[amyodov]

Crossing the fingers to see the Raspberry Pi 5 support here... Pi5 is not in the options in the Makefile, but hopefully it can be just added together with the Pi4, in a line like Pi3 Pi4 Pi5 Pi400 PiZero2 PiCM3 PiCM4: clean, and mentioned in the readme.

I actually tried to use this build script without the changes, and was able to at least build the resulting kernel8_rt.img (I didn't use the img SD card image file directly, but copied just the kernel files – your script is still the best one to build the RT RPi kernel in a docker/on a more powerful station, even if one just needs the kernel, not the whole SD card image), and that resulted in a Linux raspberrypi 6.6.31-v8+ #1 SMP without any RT, so some other tweaks may be required, too.

Also, it would be highly appreciated if you could give some hints in readme/add some extra lines in a Makefile, to avoid building the SD card image, just cross-building the kernel image (for further transfer to a live system).