Add asan-specific CleanSpec

ASAN builds run as two consecutive builds.  The cleanspec is applied by
the first one, which cleans the obj directory, and ignored by the
second.  This can result in old entries in the obj_asan directory.

Bug: 73885582
Test: obj_asan dirs are deleted
Change-Id: I54b8ec9cff581fcd9ec2a843aa7126805340c387
Merged-In: I54b8ec9cff581fcd9ec2a843aa7126805340c387
(cherry picked from commit 4e2da327)