[first introduced][require_android_5] with OkHttp 3.13.

Here’s what you need in `build.gradle` to target Java 8 byte code for Kotlin, Java, and Android
plugins respectively.

```groovy
compileKotlin {
  kotlinOptions {
    jvmTarget = "1.8"
  }
}
compileTestKotlin {
  kotlinOptions {
    jvmTarget = "1.8"
  }
}

compileJava {
  sourceCompatibility = JavaVersion.VERSION_1_8