問題点
d8/r8 does not support using custom multidex.keep files if minSdkVersion>= 21, e.g. devices where native multidex is supported. In theses cases, d8/r8 calculates the contents of the main classes.dex without rules specified by developers.
This change in d8/r8 appeared in version 1.4.93.
解決策
Verify you are not declaring any MultiDexMainDexList build items.
Consider submitting a bug if your application does not function after removing any MultiDexMainDexList items.