Fix friend paths not configured correctly with separate classes dirs

(cherry picked from commit d5ee659)

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/BaseMultiGradleVersionIT.kt

@@ -12,6 +12,6 @@ abstract class BaseMultiGradleVersionIT : BaseGradleIT() {
     companion object {
         @JvmStatic
         @Parameters(name = "Test with Gradle version {0}")
-        fun params() = listOf("2.10", "2.14.1", "3.2", "3.3", "3.4").map { arrayOf(it) }
+        fun params() = listOf("2.10", "2.14.1", "3.2", "3.3", "3.4", "4.0").map { arrayOf(it) }
     }
 }

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/KotlinGradlePluginIT.kt

@@ -171,15 +171,6 @@ class KotlinGradleIT: BaseGradleIT() {
         }
     }
 
-    @Test
-    fun testInternalTest() {
-        Project("internalTest", GRADLE_VERSION).build("build") {
-            assertSuccessful()
-            assertReportExists()
-            assertContains(":compileKotlin", ":compileTestKotlin")
-        }
-    }
-
     @Test
     fun testMultiprojectPluginClasspath() {
         Project("multiprojectClassPathTest", GRADLE_VERSION).build("build") {

libraries/tools/kotlin-gradle-plugin-integration-tests/src/test/kotlin/org/jetbrains/kotlin/gradle/KotlinGradlePluginMultiVersionIT.kt

@@ -68,4 +68,13 @@ class KotlinGradlePluginMultiVersionIT : BaseMultiGradleVersionIT() {
             assertSuccessful()
         }
     }
+
+    @Test
+    fun testInternalTest() {
+        Project("internalTest", gradleVersion).build("build") {
+            assertSuccessful()
+            assertReportExists()
+            assertContains(":compileKotlin", ":compileTestKotlin")
+        }
+    }
 }

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

@@ -139,7 +139,9 @@ abstract class AbstractKotlinCompile<T : CommonCompilerArguments>() : AbstractKo
     protected val friendTask: AbstractKotlinCompile<T>?
             get() = friendTaskName?.let { project.tasks.findByName(it) } as? AbstractKotlinCompile<T>
 
-    var friendPaths: Lazy<Array<String>?> = lazy { friendTask?.javaOutputDir?.absolutePath?.let { arrayOf(it) } }
+    var friendPaths: Lazy<Array<String>?> = lazy {
+        friendTask?.run { arrayOf((javaOutputDir ?: destinationDir).absolutePath) }
+    }
 
     override fun compile() {
         assert(false, { "unexpected call to compile()" })