message: Fix clippy::cast_abs_to_unsigned
diff: @@ -95,8 +95,8 @@ extern "C" fn __sys_sbrk(incr: isize) -> usize {
  old_end = SBRK_COUNTER.fetch_add(incr as usize, Ordering::SeqCst);
  assert!(task_heap_end.as_usize() >= old_end + incr as usize);
  } else {
  - old_end = SBRK_COUNTER.fetch_sub(incr.abs() as usize, Ordering::SeqCst);
  - assert!(task_heap_start.as_usize() < old_end - incr.abs() as usize);
  + old_end = SBRK_COUNTER.fetch_sub(incr.unsigned_abs(), Ordering::SeqCst);
  + assert!(task_heap_start.as_usize() < old_end - incr.unsigned_abs());
  }
  old_end
  