Add input for version selection?

[animetosho]

Thanks for making this action.

I noticed that the compiler version used is hardcoded based on Ubuntu version, however there's often multiple compiler versions available per Ubuntu release (e.g. Jammy supports gcc-12).
It'd be nice if the version could be overridden if desired.

Also, it might be useful to have the compiler (or $ARCHGCC) set as an output, so that they can be directly used without needing a second mapping elsewhere.