Expand the build documentation

[AlpinDale]

Moving the issue from here.

The current build instructions don't specify the system package requirements for building python with asdf on a fresh OS. Might be worth adding these, or bake it into the install script that would prompt the user with the install commands so they won't be left confused after a failed installation. Here are the five packages that are required to build python:

sudo apt-get install libffi-dev libreadline-dev libssl-dev
sudo apt-get install libsqlite3-dev liblzma-dev  # optional

[Denizzje]

Thank you, I swear this used to be documented before on this page? Did somebody remove it...