Update dart:io to convert strings between UTF8 and current code page

runtime/bin/utils_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 <errno.h>
 #include <netdb.h>
 
 #include "bin/utils.h"
 #include "platform/assert.h"
 
 OSError::OSError() : sub_system_(kSystem), code_(0), message_(NULL) {
   set_sub_system(kSystem);
   set_code(errno);
   SetMessage(strerror(errno));
 }
 
 
 void OSError::SetCodeAndMessage(SubSystem sub_system, int code) {
   set_sub_system(sub_system);
   set_code(code);
   if (sub_system == kSystem) {
     SetMessage(strerror(code));
   } else if (sub_system == kGetAddressInfo) {
     SetMessage(gai_strerror(code));
   } else {
     UNREACHABLE();
   }
 }
+
+const char* StringUtils::SystemStringToUtf8(const char* str) {
+  return str;
+}
+
+const char* StringUtils::Utf8ToSystemString(const char* utf8) {
+  return utf8;
+}
+
+char* StringUtils::SystemStringToUtf8(char* str) {
+  return str;
+}
+
+char* StringUtils::Utf8ToSystemString(char* utf8) {
+  return utf8;
+}