In rB1a4fc6dcd67b, a `return` was added in the middle of regular versioning
code, causing unintended early-exit of versioning. This can be a rather hard to
track down error, which would be good to avoid - statically if possible.
Poisoning occurrences of "return" is the only static way I can think of to do
this, and it's GCC and Clang only. Maybe this is a bit overkill because the
error is unlikely to happen often, but I'd like to have it proposed