[stdlib] Merge js-ir specific sources into common js sources

libraries/stdlib/js/runtime/dceUtils.kt

@@ -0,0 +1,16 @@
+/*
+ * Copyright 2010-2021 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 kotlin.js
+
+import JsError
+
+internal fun unreachableDeclarationLog() {
+    console.asDynamic().trace("Unreachable declaration")
+}
+
+internal fun unreachableDeclarationException() {
+    throw JsError("Unreachable declaration")
+}