[JS_IR] Use new plugin to build Kotlin/JS stdlib with IR compiler

- Switch to building stdlib with bootstrap compiler since IR is stable
  enough
- Build stdlib with coreLibs by default
- Include JS IR stdlib to kotlin distribution

libraries/stdlib/wasm/build.gradle.kts

@@ -0,0 +1,37 @@
+import org.jetbrains.kotlin.gradle.dsl.KotlinCompile
+import org.jetbrains.kotlin.gradle.plugin.KotlinJsCompilerType.IR
+import org.jetbrains.kotlin.gradle.targets.js.nodejs.NodeJsRootExtension
+import org.jetbrains.kotlin.gradle.targets.js.nodejs.NodeJsRootPlugin
+
+plugins {
+    kotlin("multiplatform")
+}
+
+kotlin {
+    js(IR) {
+        nodejs()
+    }
+    sourceSets {
+        val jsMain by getting {
+            kotlin.srcDirs("builtins", "internal", "runtime")
+        }
+    }
+}
+
+tasks.withType<KotlinCompile<*>>().configureEach {
+    kotlinOptions.freeCompilerArgs += listOf(
+        "-Xallow-kotlin-package",
+        "-Xallow-result-return-type",
+        "-Xuse-experimental=kotlin.Experimental",
+        "-Xuse-experimental=kotlin.ExperimentalMultiplatform",
+        "-Xuse-experimental=kotlin.contracts.ExperimentalContracts",
+        "-Xinline-classes",
+        "-Xopt-in=kotlin.RequiresOptIn",
+        "-Xopt-in=kotlin.ExperimentalUnsignedTypes",
+        "-Xopt-in=kotlin.ExperimentalStdlibApi"
+    )
+}
+
+tasks.named("compileKotlinJs") {
+    (this as KotlinCompile<*>).kotlinOptions.freeCompilerArgs += "-Xir-module-name=kotlin"
+}