[scudo] Add missing include for extern variable declaration am: 014e4eac6c am: 5d85400f08 am: 6b0b281ff3

Original change: https://android-review.googlesource.com/c/platform/external/scudo/+/2066951

Change-Id: I2bed40acbc8624a531a990d7ca236c30a131ef8b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>