Add a workaround for macOS to avoid serialising size_t
Add a workaround for macOS to avoid serialising size_t

* We never should have serialised size_t in the first place so this shouldn't
  have happened, but since we want to keep some semblence of best-effort
  backwards compatibility, we'll keep the code and just disable it on macOS.

TurtleRockStudios/renderdoc_public,baldurk/renderdoc,baldurk/renderdoc,baldurk/renderdoc,googlestadia/renderdoc,baldurk/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,googlestadia/renderdoc,Zorro666/renderdoc,baldurk/renderdoc,Zorro666/renderdoc,TurtleRockStudios/renderdoc_public,Zorro666/renderdoc,googlestadia/renderdoc,TurtleRockStudios/renderdoc_public,TurtleRockStudios/renderdoc_public,Zorro666/renderdoc,TurtleRockStudios/renderdoc_public,googlestadia/renderdoc,Zorro666/renderdoc,TurtleRockStudios/renderdoc_public,googlestadia/renderdoc,googlestadia/renderdoc