Really remove io support when dart:io is unsupported.

runtime/bin/platform.cc

Index: runtime/bin/platform.cc
diff --git a/runtime/bin/platform.cc b/runtime/bin/platform.cc
index 716ef2932933027b638fd1031e1d3243151886f2..2099ebb7b4edc3cfa6182c93a2d04a3fc591ce5c 100644
--- a/runtime/bin/platform.cc
+++ b/runtime/bin/platform.cc
@@ -2,21 +2,17 @@
 // 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 "bin/platform.h"
+#if !defined(DART_IO_DISABLED)
 
-#include "include/dart_api.h"
+#include "bin/platform.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()));
 }
@@ -125,3 +121,5 @@ void FUNCTION_NAME(Platform_GetVersion)(Dart_NativeArguments args) {
 
 }  // namespace bin
 }  // namespace dart
+
+#endif  // !defined(DART_IO_DISABLED)