Conditionally apply Kotlin if not using JDK 9
Conditionally apply Kotlin if not using JDK 9

Kotlin does not yet work with JDK 9, so we need to disable the Kotlin
plugin if we are using JDK 9.

spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework