aar 的生成，如果你的libary 的build.gradle中没有配置
compile(name: "jnilib-release", ext: "aar")
compile fileTree(include: ['*.jar'], dir: 'libs')
testCompile 'junit:junit:4.12'
compile files('libs/activation.jar')
compile files('libs/additionnal.jar')
compile files('libs/mail.jar')
compile files('libs/zxing.jar')
compile files('libs/android-async-http-1.4.5.jar')
右边的gradle 中是没有build等选项的