[JS IR] Support per-file mode and ES modules

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JSCompilerArguments.kt

@@ -170,6 +170,9 @@ class K2JSCompilerArguments : CommonCompilerArguments() {
     @Argument(value = "-Xir-per-module-output-name", description = "Adds a custom output name to the splitted js files")
     var irPerModuleOutputName: String? by NullableStringFreezableVar(null)
 
+    @Argument(value = "-Xir-per-file", description = "Splits generated .js per-file")
+    var irPerFile: Boolean by FreezableVar(false)
+
     @Argument(
         value = "-Xinclude",
         valueDescription = "<path>",

compiler/cli/cli-common/src/org/jetbrains/kotlin/cli/common/arguments/K2JsArgumentConstants.java

@@ -24,6 +24,7 @@ public interface K2JsArgumentConstants {
     String MODULE_AMD = "amd";
     String MODULE_COMMONJS = "commonjs";
     String MODULE_UMD = "umd";
+    String MODULE_ES = "es";
 
     String SOURCE_MAP_SOURCE_CONTENT_ALWAYS = "always";
     String SOURCE_MAP_SOURCE_CONTENT_NEVER = "never";