buildconfig=true is deprecated.

build提示

The option setting 'android.defaults.buildfeatures.buildconfig=true' is deprecated. 
The current default is 'false'.
It will be removed in version 9.0 of the Android Gradle plugin.

模块目录下的build.gradle 里面 (不是根目录),
就是分开了,用于有些model不用生成BuildConfig

android{
     buildFeatures.buildConfig = true
}