minimum scala compile settings for gradle-scala

build.grade

apply plugin: 'scala'

repositories {
  mavenCentral()
}

dependencies {
    compile 'org.scala-lang:scala-library:2.12.+'
}

HelloWorld.scala

object HelloWorld {
  def main(args: Array[String]): Unit = {
    println("Hello, world!")
  }
}

tree

.
├── build.gradle
└── src
    └── main
        └── scala
            └── Main.scala