pi-bootbuilder
pi-bootbuilder is a small docker based tool that generates the data for the boot partition for raspberry pi 3+4 (aarch64) based on u-boot. This is designed to run on every platform that supports cross-compiling to aarch64 on ubuntu:latest.
Building the docker image
$> docker build . -t pi-bootbuilder:latest
Running the build
$> docker run -v $(pwd)/output:/data/output pi-bootbuilder:latest
The contents of $(pwd)/output should then be copied to the boot partition of
the sd-card.