message: [build] add project extensions for Android.mk
diff: @@ -30,6 +30,10 @@ LOCAL_PATH := $(call my-dir)
  ifeq ($(OTBR_ENABLE_ANDROID_MK),1)
  +ifneq ($(OTBR_PROJECT_ANDROID_MK),)
  +include $(OTBR_PROJECT_ANDROID_MK)
  +endif
  +
  include $(CLEAR_VARS)
  LOCAL_MODULE_CLASS := STATIC_LIBRARIES
  @@ -131,6 +135,10 @@ LOCAL_SRC_FILES += \
  LOCAL_SHARED_LIBRARIES += libmdnssd
  endif
  +LOCAL_SRC_FILES += $(OTBR_PROJECT_SRC_FILES)
  +LOCAL_STATIC_LIBRARIES += $(OTBR_PROJECT_STATIC_LIBRARIES)
  +LOCAL_SHARED_LIBRARIES += $(OTBR_PROJECT_SHARED_LIBRARIES)
  +
  include $(BUILD_EXECUTABLE)
  include $(CLEAR_VARS)
  