[Wasm/WASI] Implementation of a callback on root exported function exit

Fixed #KT-64486

libraries/stdlib/wasm/wasi/src/kotlin/internal/internalCallback.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2010-2023 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.wasm.internal
+
+@RequiresOptIn
+private annotation class InternalWasmApi
+
+/*
+This is internal API which is not intended to use on user-side.
+ */
+@InternalWasmApi
+public var onExportedFunctionExit: (() -> Unit)? = null
+
+internal fun invokeOnExportedFunctionExit() {
+    @OptIn(InternalWasmApi::class)
+    onExportedFunctionExit?.invoke()
+}