[NFC][scudo] Avoid integer overflow in test am: 24f3bdc31d am: 16208f3568 am: 72a4a286e0 am: 82562c1128

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

Change-Id: I24a427c9e8609165f97169c9a8a54d6a103b438e