scudo: Work around gcc 8 conversion warning. am: cbd425c20d am: 68151bc633 am: 5944ec8fae am: e79f1f3e36

Original change: https://android-review.googlesource.com/c/platform/external/scudo/+/1685845

Change-Id: If716a312c12f90101d77fd57a13c198807098530