Use default compileJava9Java task to build java9 source set

libraries/kotlin.test/jvm/build.gradle

@@ -21,11 +21,9 @@ dependencies {
 
 archivesBaseName = 'kotlin-test'
 
-createCompileJava9Task(project, "compileJava9", "kotlin.test")
-
 jar {
     manifestAttributes(manifest, project, 'Test', true)
-    from compileJava9.outputs
+    from sourceSets.java9.output
 }
 
 artifacts {
@@ -45,3 +43,5 @@ compileKotlin {
 compileTestKotlin {
     kotlinOptions.freeCompilerArgs = ["-Xallow-kotlin-package"]
 }
+
+compileJava9Sources(project, 'kotlin.test')