Provide a tutorial or a document indicating how to build avr-gcc 9.3.0 from sources

Nothing really urgent nor really new, but as Ubuntu's repositories only ships a quite old version of avr-gcc (5.4.0), it could be a good thing to provide :
* A tutorial referring to https://www.nongnu.org/avr-libc/user-manual/install_tools.html and showing how to use it
* Provide a debian package, maybe on another repository with up-to-date dependencies ?

This is only to provide a more "even" experience while using this project and it will never replace the work done by the guys of nongnu.org, but maybe providing a "simple" way to build, install and use avr-gcc will ease a bit its use...