Drop deprecations: io and threading functions.

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

@@ -268,7 +268,7 @@ public open class Kotlin2JsCompile() : AbstractKotlinCompile<K2JSCompilerArgumen
             get() = kotlinOptions.outputFile
 
     public val sourceMapDestinationDir: File
-            get() = File(outputFile).directory
+            get() = File(outputFile).let { if (it.isDirectory) it else it.parentFile!! }
 
     public val sourceMap: Boolean
             get() = kotlinOptions.sourceMap
@@ -298,7 +298,7 @@ public open class Kotlin2JsCompile() : AbstractKotlinCompile<K2JSCompilerArgumen
             throw GradleException("$name.kotlinOptions.outputFile should be specified.")
         }
 
-        val outputDir = File(args.outputFile).directory
+        val outputDir = File(args.outputFile).let { if (it.isDirectory) it else it.parentFile!! }
         if (!outputDir.exists()) {
             if (!outputDir.mkdirs()) {
                 throw GradleException("Failed to create output directory ${outputDir} or one of its ancestors")

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

@@ -199,7 +199,7 @@ class Kotlin2JsSourceSetProcessor(
 
     val defaultKotlinDestinationDir = File(project.buildDir, "kotlin2js/${sourceSetName}")
     private fun kotlinTaskDestinationDir(): File? = kotlinTask.property("kotlinDestinationDir") as File?
-    private fun kotlinJsDestinationDir(): File? = (kotlinTask.property("outputFile") as String).let { File(it).directory }
+    private fun kotlinJsDestinationDir(): File? = (kotlinTask.property("outputFile") as String).let { File(it) }.let { if (it.isDirectory) it else it.parentFile }
 
     private fun kotlinSourcePathsForSourceMap() = sourceSet.getAllSource()
             .map { it.path }