[Gradle, JS] Move JsCompilerType to Gradle Plugin API

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

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * 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.plugin
+
+import org.gradle.api.Named
+import java.io.Serializable
+
+// For Gradle attributes
+@Suppress("EnumEntryName")
+enum class JsCompilerType : Named, Serializable {
+    legacy,
+    ir,
+    both;
+
+    override fun getName(): String =
+        name.toLowerCase()
+
+    override fun toString(): String =
+        getName()
+
+    companion object {
+        const val jsCompilerProperty = "kotlin.js.compiler"
+
+        fun byArgument(argument: String): JsCompilerType? =
+            JsCompilerType
+                .values().firstOrNull { it.name.equals(argument, ignoreCase = true) }
+    }
+}