[gradle-plugin] Fix paths for source and javadoc jars

tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/experimental/internal/AbstractKotlinNativeComponent.kt

@@ -89,8 +89,8 @@ abstract class AbstractKotlinNativeComponent @Inject constructor(
         poms.add(action)
     }
 
-    override val publishJavadoc: Boolean = true
-    override val publishSources: Boolean = true
+    override var publishJavadoc: Boolean = true
+    override var publishSources: Boolean = true
 
     // endregion
 }

tools/kotlin-native-gradle-plugin/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/experimental/plugins/KotlinNativePlugin.kt

@@ -195,6 +195,7 @@ class KotlinNativePlugin @Inject constructor(val attributesFactory: ImmutableAtt
 
     private fun KotlinNativeSourceSetImpl.createSourcesJarTask(target: KonanTarget): Jar =
             createJarTask("sourcesJar${name.capitalize()}${target.name.capitalize()}") {
+                it.destinationDir = project.buildDir.resolve("libs")
                 it.appendix = "$name-${target.name}"
                 it.classifier = "sources"
                 it.from(getAllSources(target))
@@ -202,6 +203,7 @@ class KotlinNativePlugin @Inject constructor(val attributesFactory: ImmutableAtt
 
     private fun KotlinNativeSourceSetImpl.createEmptyJarTask(namePrefix: String, classifier: String): Jar =
             createJarTask("$namePrefix${name.capitalize()}") {
+                it.destinationDir = project.buildDir.resolve("libs")
                 it.appendix = name
                 it.classifier = classifier
             }