Track inter-project IC changes for Java

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/compilerRunner/GradleKotlinCompilerRunner.kt

@@ -361,6 +361,7 @@ internal class GradleCompilerRunner(private val project: Project) : KotlinCompil
                 for (task in project.tasks.withType(KotlinCompile::class.java)) {
                     val module = IncrementalModuleEntry(project.path, task.moduleName, project.buildDir, task.buildHistoryFile)
                     dirToModule[task.destinationDir] = module
+                    task.javaOutputDir?.let { dirToModule[it] = module }
                     nameToModules.getOrPut(module.name) { HashSet() }.add(module)
                 }
             }

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinPlugin.kt

@@ -632,6 +632,8 @@ abstract class AbstractAndroidProjectHandler<V>(private val kotlinConfigurationT
 }
 
 internal fun configureJavaTask(kotlinTask: KotlinCompile, javaTask: AbstractCompile, logger: Logger) {
+    kotlinTask.javaOutputDir = javaTask.destinationDir
+
     // Gradle Java IC in older Gradle versions (before 2.14) cannot check .class directories updates.
     // To make it work, reset the up-to-date status of compileJava with this flag.
     kotlinTask.anyClassesCompiled = false

libraries/tools/kotlin-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/tasks/Tasks.kt

@@ -185,10 +185,15 @@ abstract class AbstractKotlinCompile<T : CommonCompilerArguments>() : AbstractKo
     @get:Internal // takes part in the compiler arguments
     var friendPaths: Lazy<Array<String>?> = lazy {
         friendTask?.let { friendTask ->
-            mutableListOf<String>().apply {
-                add((friendTask.javaOutputDir ?: friendTask.destinationDir).absolutePath)
-                addAll(friendTask.attachedClassesDirs.mapNotNull { it.value?.absolutePath })
-            }.toTypedArray()
+            val possibleFriendDirs = ArrayList<File?>().apply {
+                add(friendTask.javaOutputDir)
+                add(friendTask.destinationDir)
+                addAll(friendTask.attachedClassesDirs.map { it.value })
+            }
+
+            possibleFriendDirs.filterNotNullTo(HashSet())
+                .map { it.absolutePath }
+                .toTypedArray()
         }
     }