radxa/rockpi4-android-tv-7.1 — reverse-engineered prompt

I want this repo turned into a repeatable build setup that can produce Android TV 7.1 firmware images for a Rock Pi 4B, ideally from a clean Ubuntu machine or the included container setup. Please wire it up so someone can sync the source, build u boot, build the kernel, build the Android TV system, and then package the final images like boot.img, system.img, recovery.img, gpt.img, and the other files needed to flash the board.

Make the process as close to one command as possible, but keep the individual steps available too. Please include clear setup notes for the required Java 8 and build tools, mention that the full source download is very large, and add straightforward instructions for flashing to a TF card, eMMC, or over rockusb. If anything in the repo is incomplete, fill in the missing glue scripts and documentation so a normal person can actually use it. You can look up current docs online if you need to.