[clang] label diagnosed as unused when used with `break` and/or `continue` (C2Y named loop)

[olemayu]

https://godbolt.org/z/9bE1Yv4s9

loop: // warning: unused label 'loop' [-Wunused-label]
while (true) {
    Event event;

    while (PollEvent(&event)) {
        if (event.type == EVENT_QUIT) {
            break loop;
        }
    }
}

[shafik]

CC @Sirraide @AaronBallman