vonbrand pretty much stated the obvious here, but I'll go ahead and bite for a bit, and explain why you're off base in your hypothetical situation.
So, let's say someone did try to do this, how does the GPL protect us? Well, the only feasible way this could be done would be with an automated script.
In this case, someone went from human-readable code -> "meta-c" code (using automated script) -> C compiler -> binary. The "source" chain still starts at the original unmangled C files. You could also argue that the organization that did this would have to release their mangling script too, since it's part of the required build materials. In short, it'd blow up on them in a bad way.