This is the Zyxel VMG8825-B50B firmware buildsystem.

Follow these steps to build a base/standard firmware

Build a docker compile environment:
 docker build . -t vmg8825_b50b:ubuntu-12.04

Run a container:
 docker run -it --rm -u 1000:1000 --name builder -v "$PWD":/app vmg8825_b50b:ubuntu-12.04

Set the default project to compile:
 export P=vmg8825_b50b

Start compiling (note that -j flag is not supported):
 make

You can flash ras.bin from your router web interface