Ensure default toolchain is also set to java only modules.

^KT-46972 Fixed

buildSrc/src/main/kotlin/JvmToolchain.kt

@@ -43,6 +43,9 @@ fun Project.shouldOverrideObsoleteJdk(
 fun Project.configureJvmToolchain(
     jdkVersion: JdkMajorVersion
 ) {
+    // Ensure java only modules also set default toolchain
+    configureJavaOnlyToolchain(jdkVersion)
+
     plugins.withId("org.jetbrains.kotlin.jvm") {
         val kotlinExtension = extensions.getByType<KotlinTopLevelExtension>()
 

prepare/compiler/build.gradle.kts

@@ -11,7 +11,6 @@ plugins {
     java
 }
 
-val JDK_18: String by rootProject.extra
 
 val fatJarContents by configurations.creating {
     isCanBeResolved = true