Never add asan libraries to NDK code

We're beginning to enforce (still warning) that NDK code only links to
other NDK code. So we should never need to link them to the address
sanitizer libraries.

This breaks down a bit when platform code starts depending on NDK-built
code, where the NDK-built code should be mostly the same as if it was
built with the platform, but has an implicit LOCAL_SANITIZE := never.
Even so, this change shouldn't make that worse, as we'll still compile
fine, and anything platform code that uses asan should pull in the
shared library.

Change-Id: I81b30b9edd971468c3cb1467f809f184807b505e