在buildSrc下的build.gradle中添加如下依赖，用来查看其源码并debug
dependencies {
implementation("com.android.tools.build:gradle:3.2.1")
}
源码为于External Libraries中:
Gradle: gradle-3.2.1 其META-INF中定义了多个android plugin的入口Class如com.android.application的入口com.android.build.gradle.AppPlugin
Gradle: gradle-api-3.2.1 AppExtension定义在这
Gradle: builder-3.2.1，d8,r8源码都在此处
而gradle源码(gradle/wrapper/gradle-wrapper.properties中定义的gradle版本)
distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.4-all.zip
位于External Libraries中:
Gradle: gradle-api-5.6.4