gradle-plugin: Annotate properties not used for UP-TO-DATE check

This patch annotates all task properties which are not used for
UP-TO-DATE checks with Gradle's @Internal annotation (see https://
docs.gradle.org/4.0/javadoc/org/gradle/api/tasks/Internal.html) to
fix Gradle validation warnings.

tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KonanCompileTask.kt

@@ -73,31 +73,32 @@ open class KonanCompileTask: KonanTargetableTask() {
     }
 
     val COMPILER_JVM_ARGS: List<String>
-        get() = listOf("-Dkonan.home=${project.konanHome}", "-Djava.library.path=${project.konanHome}/konan/nativelib")
+        @Internal get() = listOf("-Dkonan.home=${project.konanHome}", "-Djava.library.path=${project.konanHome}/konan/nativelib")
     val COMPILER_CLASSPATH: String
-        get() = "${project.konanHome}/konan/lib/"
+        @Internal get() = "${project.konanHome}/konan/lib/"
 
     // Output artifact --------------------------------------------------------
 
     internal lateinit var artifactName: String
+        @Internal get
 
-    lateinit var outputDir: File
+    @Internal lateinit var outputDir: File
         internal set
 
     internal fun init(artifactName: String) {
         dependsOn(project.konanCompilerDownloadTask)
         this.artifactName = artifactName
-        outputDir = project.file("${project.konanCompilerOutputDir}")
+        outputDir = project.file(project.konanCompilerOutputDir)
     }
 
     val artifactNamePath: String
-        get() = "${outputDir.absolutePath}/$artifactName"
+        @Internal get() = "${outputDir.absolutePath}/$artifactName"
 
     val artifactSuffix: String
-        get() = produceSuffix(produce)
+        @Internal get() = produceSuffix(produce)
 
     val artifactPath: String
-        get() = "$artifactNamePath$artifactSuffix"
+        @Internal get() = "$artifactNamePath$artifactSuffix"
 
     val artifact: File
         @OutputFile get() = project.file(artifactPath)

tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KonanInteropTask.kt

@@ -54,9 +54,9 @@ open class KonanInteropTask: KonanTargetableTask() {
     }
 
     internal val INTEROP_JVM_ARGS: List<String>
-        get() = listOf("-Dkonan.home=${project.konanHome}", "-Djava.library.path=${project.konanHome}/konan/nativelib")
+        @Internal get() = listOf("-Dkonan.home=${project.konanHome}", "-Djava.library.path=${project.konanHome}/konan/nativelib")
     internal val INTEROP_CLASSPATH: String
-        get() = "${project.konanHome}/konan/lib/"
+        @Internal get() = "${project.konanHome}/konan/lib/"
 
     // Output directories -----------------------------------------------------
 

tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KonanTargetableTask.kt

@@ -29,15 +29,16 @@ abstract class KonanTargetableTask: DefaultTask() {
 
     internal val targetManager: TargetManager by lazy {
         TargetManager(target ?: "host")
-    }
+    } @Internal get
+
 
     val targetIsSupported: Boolean
-        get() = targetManager.target.enabled
+        @Internal get() = targetManager.target.enabled
 
     val isCrossCompile: Boolean
-        get() = (targetManager.target != TargetManager.host)
+        @Internal get() = (targetManager.target != TargetManager.host)
 
-    fun produceSuffix(produce: String): String 
+    @Internal fun produceSuffix(produce: String): String
         = CompilerOutputKind.valueOf(produce.toUpperCase())
             .suffix(targetManager.target)
 }