Simple CSS that leaves only clang (trunk), gcc (snapshot) and CL 2017 in the dropdown list on godbolt.
To use, import this in the "Stylish" extension in Chrome/Firefox (I guess, didn't try it myself).
I rarely use other compilers, so this is tailored for me. In case another compiler is needed, either disable Stylish, or blindly type a substring of its name and hit Down + Enter.
I don't know CSS, so patches are welcome if needed.