message: Add message before dumping alloc
diff: @@ -118,7 +118,12 @@ pub fn report_error<'tcx, 'mir>(
  let result = report_msg(ecx, &format!("{}: {}", title, msg), msg, helps, true);
  if let UndefinedBehavior(UndefinedBehaviorInfo::InvalidUndefBytes(Some(ptr))) = e.kind {
  + eprintln!(
  + "Uninitialized read occurred at offset 0x{:x} into this allocation:",
  + ptr.offset.bytes(),
  + );
  ecx.memory.dump_alloc(ptr.alloc_id);
  + eprintln!();
  }
  result
  