升级为android studio3.0，gradle升级为4.1，报错：
A failure occurred while executing com.android.build.gradle.tasks.MergeResources$FileGenerationWorkAction
> Error while processing D:\Android\WeishuProjects\Zszy\app\src\main\res\drawable\ic_right_gray_24dp.xml : Can't process attribute android:fillColor="@color/text_gray": references to other resources are not supported by build-time PNG generation.
