Declare dlmalloc as a cc_library_headers am: 6d7299810b am: 1ae0a0aedd am: d0c75b05e5

Original change: https://android-review.googlesource.com/c/platform/external/dlmalloc/+/2139492

Change-Id: Ic62cef7bfe72e5c50c45d5860130df32485ad2dd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>