Simplify process exit-code handling on Posix, take 2.

runtime/bin/platform_macos.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include "bin/platform.h"
 
 #include <crt_externs.h>  // NOLINT
 #include <signal.h>  // NOLINT
 #include <string.h>  // NOLINT
 #include <unistd.h>  // NOLINT
 
 
 namespace dart {
 namespace bin {
 
 bool Platform::Initialize() {
   // Turn off the signal handler for SIGPIPE as it causes the process
   // to terminate on writing to a closed pipe. Without the signal
   // handler error EPIPE is set instead.
   struct sigaction act;
   bzero(&act, sizeof(act));
   act.sa_handler = SIG_IGN;
   if (sigaction(SIGPIPE, &act, 0) != 0) {
     perror("Setting signal handler failed");
     return false;
   }
-  // Unblock SIGCHLD as waiting on spawned child process depends
-  // on successful interception of this signal.
-  sigset_t newset;
-  sigemptyset(&newset);
-  sigaddset(&newset, SIGCHLD);
-  if (sigprocmask(SIG_UNBLOCK, &newset, NULL) != 0) {
-    perror("Unblocking SIGCHLD signal failed");
-  }
-
   return true;
 }
 
 
 int Platform::NumberOfProcessors() {
   return sysconf(_SC_NPROCESSORS_ONLN);
 }
 
 
 const char* Platform::OperatingSystem() {
@@ skipping 25 matching lines @@
 
 
 void Platform::FreeEnvironment(char** env, intptr_t count) {
   delete[] env;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)