Here are the steps to setup mgba as well as the development tools that you'll need to build GBA roms on your Raspberry Pi. I did this on a Pi4, but it should work on a Pi3 or even a Pi2 just as well.
-
un-comment the sources repo in /etc/apt/sources.list using your editor of choice (requires root of course).
-
sudo apt-get update
to get fresh sources info -
sudo apt build-dep mgba-qt
to install all the dependencies of the Qt