Use libxml2 as shared lib.

The dependencies to static libraries in frameworks should be removed
as many as possible to reduce a size of the system partition.
And that will improve coverage of the VNDK libraries because this
effort might find new necessary shared libs which were linked
statically before.

Size diffs of affected binaries on sailfish-userdebug build are as
follows.

libaudiopolicymanagerdefault.so: 583440 -> 267288 (-316152)
libaudiopolicymanager.so       : 16008 -> 16004 (-4)

total                          : (-316156)

Test: building succeeded, and the image was tested on sailfish.
Bug: 33056637
Change-Id: I51d98c5c2b5d94561190a1651063737fb1cb06ff
diff --git a/services/audiopolicy/Android.mk b/services/audiopolicy/Android.mk
index a1420ff..7cd2b81 100644
--- a/services/audiopolicy/Android.mk
+++ b/services/audiopolicy/Android.mk
@@ -79,9 +79,7 @@
 LOCAL_SHARED_LIBRARIES += libmedia_helper
 
 ifeq ($(USE_XML_AUDIO_POLICY_CONF), 1)
-LOCAL_STATIC_LIBRARIES += libxml2
-
-LOCAL_SHARED_LIBRARIES += libicuuc
+LOCAL_SHARED_LIBRARIES += libicuuc libxml2
 
 LOCAL_CFLAGS += -DUSE_XML_AUDIO_POLICY_CONF
 endif #ifeq ($(USE_XML_AUDIO_POLICY_CONF), 1)