location: Fix incorrect unused argument workaround

 * Assigning a variable to itself causes Clang to throw an error.
 * The correct way to do this is a cast to void (the original issue was
   that it was cast to a void* instead of void, causing the 64-bit
   compilation failure)

Change-Id: I4773c701aca7aa9bd9bb0faa6dfd425635b0dc11