libttspico should be optional, installed only when PicoTts is.

Change-Id: I6b5b81dc2c18d8a2b96074080304bfbdbc479fdc
diff --git a/pico/Android.mk b/pico/Android.mk
index 16c38d3..41ad1d3 100755
--- a/pico/Android.mk
+++ b/pico/Android.mk
@@ -16,7 +16,7 @@
     $(call all-java-files-under, compat)
 
 LOCAL_PACKAGE_NAME := PicoTts
-LOCAL_REQUIRED_MODULES := libttscompat
+LOCAL_REQUIRED_MODULES := libttscompat libttspico
 
 LOCAL_PROGUARD_FLAG_FILES := proguard.flags
 
@@ -54,6 +54,8 @@
 LOCAL_PATH:= $(TOP_LOCAL_PATH)/tts
 include $(CLEAR_VARS)
 
+LOCAL_MODULE_TAGS := optional
+
 LOCAL_SRC_FILES:= com_svox_picottsengine.cpp svox_ssml_parser.cpp
 LOCAL_C_INCLUDES += \
 	external/svox/pico/lib \