Really remove io support when dart:io is unsupported.

runtime/bin/platform.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.
 
+#if !defined(DART_IO_DISABLED)
+
 #include "bin/platform.h"
 
-#include "include/dart_api.h"
-
 #include "bin/file.h"
 #include "bin/utils.h"
+#include "include/dart_api.h"
 
 namespace dart {
 namespace bin {
 
-const char* Platform::executable_name_ = NULL;
-char* Platform::resolved_executable_name_ = NULL;
-int Platform::script_index_ = 1;
-char** Platform::argv_ = NULL;
-
 void FUNCTION_NAME(Platform_NumberOfProcessors)(Dart_NativeArguments args) {
   Dart_SetReturnValue(args, Dart_NewInteger(Platform::NumberOfProcessors()));
 }
 
 
 void FUNCTION_NAME(Platform_OperatingSystem)(Dart_NativeArguments args) {
   Dart_SetReturnValue(args, DartUtils::NewString(Platform::OperatingSystem()));
 }
 
 
@@ skipping 88 matching lines @@
   }
 }
 
 
 void FUNCTION_NAME(Platform_GetVersion)(Dart_NativeArguments args) {
   Dart_SetReturnValue(args, Dart_NewStringFromCString(Dart_VersionString()));
 }
 
 }  // namespace bin
 }  // namespace dart
+
+#endif  // !defined(DART_IO_DISABLED)