Add a new root of <...>.dsl.KotlinCompile hierarchy in API

This new interface uses a more general type for its kotlinOptions,
KotlinCommonToolOptions rather than KotlinCommonOptions. This is
needed for the Kotlin/Native task to implement a common interface
with the other Kotlin compilation tasks.

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/dsl/KotlinCompile.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.gradle.dsl
+
+import groovy.lang.Closure
+import org.gradle.api.Task
+import org.gradle.api.tasks.Internal
+
+interface KotlinCompile<out T : KotlinCommonOptions> : Task {
+    @get:Internal
+    val kotlinOptions: T
+
+    fun kotlinOptions(fn: T.() -> Unit) {
+        kotlinOptions.fn()
+    }
+
+    fun kotlinOptions(fn: Closure<*>) {
+        fn.delegate = kotlinOptions
+        fn.call()
+    }
+}

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

@@ -18,21 +18,6 @@ package org.jetbrains.kotlin.gradle.dsl
 
 import groovy.lang.Closure
 import org.gradle.api.Task
-import org.gradle.api.tasks.Internal
-
-interface KotlinCompile<T : KotlinCommonOptions> : Task {
-    @get:Internal
-    val kotlinOptions: T
-
-    fun kotlinOptions(fn: T.() -> Unit) {
-        kotlinOptions.fn()
-    }
-
-    fun kotlinOptions(fn: Closure<*>) {
-        fn.delegate = kotlinOptions
-        fn.call()
-    }
-}
 
 interface KotlinJsCompile : KotlinCompile<KotlinJsOptions>