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

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

Change-Id: Ibff3705457c8cc5c2850ad93be4c0b45d0ce78a8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>