I decided to download the precompiled installer, and extract the "Install Certificates.command" from it, then store the Python code it contains into a "installcerts.py" file (only the Python code, excluding a few non-Python lines), and then run "python3 ./installcerts.py"
It worked fine, but this should be documented somewhere, for users wanting to build from source on MacOS.
It worked fine, but this should be documented somewhere, for users wanting to build from source on MacOS.