Fix validation warning for Kotlin/Native compilation task

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

@@ -58,8 +58,8 @@ open class KotlinNativeCompile : DefaultTask() {
     val additionalCompilerOptions: Collection<String>
         @Input get() = compilation.extraOpts
 
-
-    @OutputFile
+    // We manually register this property as output file or directory depending on output kind.
+    @Internal
     val outputFile: Property<File> = project.objects.property(File::class.java)
 
     // endregion