project
  |
  |---app->main.cpp, Android.mk
  |
  |---lib->|->Android.mk
           |
           |---include----|
           |              |---mylib->a.h, b.h ...
           |
           |---libs-> libX.so, libY.so, libZ.so

#include <mylib/a.h>
#include <mylib/b.h>

LOCAL_PATH             := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE           :=  my_application
LOCAL_SHARED_LIBRARIES := the_libX_1_0_0 the_libY_1_0_0 the_libZ_0_0_9
LOCAL_SRC_FILES        := main.cpp
include $(BUILD_SHARED_LIBRARY)

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE                := the_libX_1_0_0
LOCAL_C_INCLUDES            := $(LOCAL_PATH)/include
LOCAL_SRC_FILES             := $(LOCAL_PATH)/libs/libX.so
LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
include $(BUILD_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE                := the_libY_1_0_0
LOCAL_C_INCLUDES            := $(LOCAL_PATH)/include
LOCAL_SRC_FILES             := $(LOCAL_PATH)/libs/libY.so
LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
include $(BUILD_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE                := the_libZ_0_0_9
LOCAL_C_INCLUDES            := $(LOCAL_PATH)/include
LOCAL_SRC_FILES             := $(LOCAL_PATH)/libs/libZ.so
LOCAL_EXPORT_C_INCLUDE_DIRS := $(LOCAL_PATH)/include
include $(BUILD_SHARED_LIBRARY)

including ./Android.mk ...
build/core/binary.mk:1345: *** project/lib/Android.mk: the_libX_1_0_0: Unused source files: project/lib/libs/the_libX_1_0_0.so.
build/core/ninja.mk:155: recipe for target 'out/build-aosp_arm.ninja' failed
make: *** [out/build-aosp_arm.ninja] Error 1