Remove unneeded zeroing TLS (#4480)

kotlin-native/backend.native/tests/build.gradle

@@ -1044,6 +1044,12 @@ task worker11(type: KonanLocalTest) {
     source = "runtime/workers/worker11.kt"
 }
 
+standaloneTest("worker_threadlocal_no_leak") {
+    disabled = project.globalTestArgs.contains('-opt') || (project.testTarget == 'wasm32') // Needs debug build and pthreads.
+    source = "runtime/workers/worker_threadlocal_no_leak.kt"
+    flags = ['-g']
+}
+
 task freeze0(type: KonanLocalTest) {
     enabled = (project.testTarget != 'wasm32') // No workers on WASM.
     goldValue = "frozen bit is true\n" +

kotlin-native/backend.native/tests/runtime/workers/worker_threadlocal_no_leak.kt

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2010-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+import kotlin.native.concurrent.*
+
+@ThreadLocal
+var x = Any()
+
+fun main() {
+    val worker = Worker.start()
+
+    worker.execute(TransferMode.SAFE, {}) {
+        println(x)  // Make sure x is initialized
+    }.result
+
+    worker.requestTermination().result
+}