If you're going to go to the effort of writing the complement version instead of pragma-suppressing the warning on that line, just remove the ifdef and use that with all compilers.
Then I would look like someone who doesn't know that unary minus on an unsigned int obtains the two's complement. That aspect can be taken care of by a comment. Why I might go for the #ifdef is to avoid changing working code, except for that one compiler that is complaining.