To compile up this extension for Greenstone3, first get setup with
a self-contained Python3:

    cd <GS3-HOME>
    cd ext-cli
    ./get-selfcontained-python3.sh
    cd ..
    . ./gs3-setup-cli.sh

Then:

    pip3 install meson ninja

You're now ready to compile everything up:

    ./CASCADE-MAKE3.sh