Fix emulator audio.

Audio support was compiled in, but never initialized because
the hardware init function is in a different module and required
HAS_AUDIO to be defined too.

Change-Id: I57eccfb3a0abea86c29a9046f9f35d482a99c1f5
diff --git a/Makefile.target b/Makefile.target
index 8006c8d..7681dba 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -103,6 +103,9 @@
 LOCAL_CFLAGS += $(ZLIB_CFLAGS)
 endif
 
+# required to ensure we properly initialize virtual audio hardware
+LOCAL_CFLAGS += -DHAS_AUDIO
+
 ifeq ($(EMULATOR_TARGET_ARCH),x86)
 HW_SOURCES += \
     apic.c \