src/sbt-test/kotlin/basic/project/plugins.sbt

sys.props.get("plugin.version") match {
  case Some(version) => addSbtPlugin("org.jetbrains.scala" % "sbt-kotlin-plugin" % version)
  case _ => sys.error(
    """The system property 'plugin.version' is not defined.
      |Specify this property using the scriptedLaunchOpts -Dplugin.version.""".stripMargin)
}