Kotlin compile “ERROR: The Android Gradle plugin supports only Kotlin Gradle plugin version 1.3.0 and higher.” but no kotlin_version in build.gradle?

Define your ext.kotlin_version

Your project level build.gradle should look like this.

buildscript {
    ext.kotlin_version = '1.2.51'
    ext.android_plugin_version = '3.2.1'
    repositories {
        google()
        jcenter()
    }
    dependencies {
        classpath "com.android.tools.build:gradle:$android_plugin_version"
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}