add gnat ada compiler

[ghost]

do you plan on adding the Ada language compiler, present on the original GCC?

[punowo]

@brechtsanders How much of an overhead / trouble would be including Ada support ? GNAT Community was discontinued some time last year [1][2] and for Windows users the only option would be msys2.

Edit: Of course right now you can still find the last release of GNAT community edition online or go for something like https://github.com/alire-project/GNAT-FSF-builds/releases, I'm talking more in the general sense.

1. https://blog.adacore.com/a-new-era-for-ada-spark-open-source-community
2. https://alire.ada.dev/transition_from_gnat_community.html