Building System App With Prebuilt .so Library

I've been stuck here for a week trying to build a 3rd party .so library along with my app into custom Android system. I followed http://www.maxters.net/2012/05/adding-prebuilt-shared-library-to-android-build-system/ and successfully add the .so lib as prebuilt shared library to Android Build System. Now I can see the .so lib at ../out/target/product/crespo4g/obj/lib/.

But the libraries in this directory are not going to be migrated to device when flashing. And my .so lib is not appeared at /data/data/my_app_name/lib either. So UnsatisfiedLinkError occurs when executing System.loadLibrary().

I thought there are three ways to solve this, but just don't know how to implement:

Maybe my app failed to indicate to compiler that my .so is along with my app as a whole, so the .so lib is not compiled into the system image with my app. But I did declare by "LOCAL_STATIC_LIBRARIES := libXX", anything wrong?
Is there a way to build my .so lib into /system/lib/? Where are the so libs under /system/lib/ derived from?

I am new to Android building, please help..

Thanks!

You might want to check you makefile against advice in this answer and this one as well as the advice in this groups thread

UPDATE My original makefile was incorrect but this does work for me building ICS:

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libmozglue
LOCAL_SRC_FILES := libmozglue.so
LOCAL_MODULE_SUFFIX := .so
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_TAGS := optional
include $(BUILD_PREBUILT)

include $(CLEAR_VARS)
LOCAL_MODULE := libplugin-container
LOCAL_SRC_FILES := libplugin-container.so
LOCAL_MODULE_SUFFIX := .so
LOCAL_MODULE_CLASS := SHARED_LIBRARIES
LOCAL_MODULE_TAGS := optional
include $(BUILD_PREBUILT)

where the above are the native libraries required by firefox for android that I include as a system app in my custom system build.