Fix unused variable warning. am: ae97b9296b am: d9dbec9512

Original change: https://android-review.googlesource.com/c/platform/external/dlmalloc/+/3021330

Change-Id: Ib7d2422274a350d6d95929a155125373f006167a
Signed-off-by: Automerger Merge Worker <[email protected]>