Fix unused variable warning. am: ae97b9296b

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

Change-Id: I5b764bad46c87a79f1eda445c6818292e07d26bb
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>