can't find referenced method 'int checkSelfPermission(java.lang.String) 混淆失败的问题

在用腾讯的X5浏览器内核更换Android系统的WebView时，增加的SDK，混淆时报错

can't find referenced method 'int checkSelfPermission(java.lang.String)

现在越来越多的SDK开始兼容Android M,就会使用一些M里的新API,checkSelfPermission就是一个,如果本地环境没有配置成23,就会出混淆失败.错误类似下面:

Warning: u.aly.bt: can't find referenced method 'int checkSelfPermission(Java.lang.String)'
in library class android.content.Context

Warning: there were 1 unresolved references to library class members.

         You probably need to update the library versions.

         (http://proguard.sourceforge.NET/manual/troubleshooting.html#unresolvedlibraryclassmember)

Exception while processing task 

java.io.IOException: Please correct the above warnings first.

        at proguard.Initializer.execute(Initializer.java:473)

        at proguard.ProGuard.initialize(ProGuard.java:233)

        at proguard.ProGuard.execute(ProGuard.java:98)

        at proguard.gradle.ProGuardTask.proguard(ProGuardTask.java:1074)

        at com.android.build.gradle.tasks.AndroidProGuardTask.doMinification(AndroidProGuardTask.java:139)

        at com.android.build.gradle.tasks.AndroidProGuardTask$1.run(AndroidProGuardTask.java:115)

        at com.android.builder.tasks.Job.runTask(Job.java:48)

        at com.android.build.gradle.tasks.SimpleWorkQueue$EmptyThreadContext.runTask(SimpleWorkQueue.java:41)

        at com.android.builder.tasks.WorkQueue.run(WorkQueue.java:227)

        at java.lang.Thread.run(Thread.java:745)

其实知道原因之后解决就简单了,将本地编译环境改为23即可