All this commands has to be run from the root of the repository.

Run the Buildroot container:

./build.sh

In the container, copy the configuration files from the host:

cp -r /pg-wasm/* /pg-wasm/.config .

Eventually tweak the configuration and save it back to the host:

make menuconfig
cp .config /pg-wasm/.config

Build the image and save it to the host:

make