audiopolicy: Add MULTILIB statement into makefile

This fixes builds that have only 32-bit or 64-bit version
of audio server libraries.

Test: build
Change-Id: I4dc3bbe2e266a0b24d25ac00a8a2b54382b76e3d
diff --git a/services/audiopolicy/tests/Android.mk b/services/audiopolicy/tests/Android.mk
index 62869a4..a43daea 100644
--- a/services/audiopolicy/tests/Android.mk
+++ b/services/audiopolicy/tests/Android.mk
@@ -27,4 +27,6 @@
 
 LOCAL_CFLAGS := -Werror -Wall
 
+LOCAL_MULTILIB := $(AUDIOSERVER_MULTILIB)
+
 include $(BUILD_NATIVE_TEST)