How to compile pyav on platforms without available binaries.

Overview

I have a need to build pyav on the raspberry pi platform, so I need to build pyav using ffmpeg sources. What is the process for building?

For building, do I need to have ffmpeg and libraries installed in a special way, such as with the --shared flag?

There is a similar project, ffpyplayer, that has specific instructions on how to compile; it requires ffmpeg to be built with the --shared flag. https://matham.github.io/ffpyplayer/installation.html

If we can work through it here, I'll happily submit a PR to enhance the README for future users.

Thanks!