[NFC][scudo] Avoid integer overflow in test am: 24f3bdc31d am: 16208f3568 am: 72a4a286e0

Original change: https://android-review.googlesource.com/c/platform/external/scudo/+/1726993

Change-Id: I7b213e51dcbdd82b19b1f8d97ac28a0aea85e2bf