Fix patch file return types

runtime/bin/process_patch.dart

 // Copyright (c) 2013, 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.
 
 patch class _WindowsCodePageDecoder {
   /* patch */ static String _decodeBytes(List<int> bytes)
       native "SystemEncodingToString";
 }
 
 
@@ skipping 13 matching lines @@
 
   /* patch */ static Future<ProcessResult> run(String executable,
                                                List<String> arguments,
                                                [ProcessOptions options]) {
     return _runNonInteractiveProcess(executable, arguments, options);
   }
 }
 
 
 patch class _ProcessUtils {
-  /* patch */ static _exit(int status) native "Process_Exit";
-  /* patch */ static _setExitCode(int status) native "Process_SetExitCode";
-  /* patch */ static _sleep(int millis) native "Process_Sleep";
-  /* patch */ static _pid(Process process) native "Process_Pid";
+  /* patch */ static void _exit(int status) native "Process_Exit";
+  /* patch */ static void _setExitCode(int status)
+      native "Process_SetExitCode";
+  /* patch */ static void _sleep(int millis) native "Process_Sleep";
+  /* patch */ static int _pid(Process process) native "Process_Pid";
 }
 
 
 class _ProcessStartStatus {
   int _errorCode;  // Set to OS error code if process start failed.
   String _errorMessage;  // Set to OS error message if process start failed.
 }
 
 
 class _ProcessImpl extends NativeFieldWrapperClass1 implements Process {
@@ skipping 284 matching lines @@
   const _ProcessResult(int this.pid,
                        int this.exitCode,
                        String this.stdout,
                        String this.stderr);
 
   final int pid;
   final int exitCode;
   final String stdout;
   final String stderr;
 }