adding a supported compiler

[René J.V. Bertin]

Morning!

I've created a port for clazy (https://github.com/KDE/clazy) which provides an additional layer of code analysis on top of what clang already can do.

This is a compiler wrapper, so it can be used in a normal build cycle to get additional diagnostics while building code. I'd like to be able therefore to do something like `configure.compiler=clazy-3.9` for certain of my projects, at least locally.

Where would I make the necessary changes to make that possible?

Thanks,
R.