Add libaudiohal to mainline system image

32-bit libaudiohal is used by 3rd party modules on the system
partition which get loaded by client apps. In the long term,
this dependency has to be eliminated, see b/142811260.

Bug: 141989952
Bug: 142811260
Test: vendor/google/build/build_test.bash
Change-Id: I41241922c7e48c5d8bf95363944932569cb20c0a