Never use ASAN.

Unless we completely redo how we build bionic (so that the object
files for libc.so get built separately from libc.a), we can't enable
ASAN here, as libc.a gets linked into static executables.

Change-Id: I2ce4f51248bd51c4213a555ff481b6faabbf53f8
Merge "Never use ASAN."