[GWP-ASan] Respect GWP_ASAN_DEFAULT_ENABLED compile-time macro am: a9d446537a am: a59e5958bc

Original change: https://android-review.googlesource.com/c/platform/external/gwp_asan/+/1506414

Change-Id: I45e9bb5e97e020a191e8395aaa3a196e50cc3594