Really remove io support when dart:io is unsupported.

runtime/bin/platform_win.cc

Index: runtime/bin/platform_win.cc
diff --git a/runtime/bin/platform_win.cc b/runtime/bin/platform_win.cc
index 78f6cdc579ea5e4f196ef258699a91463ac2472a..8c9ab33f2e0a9a33ea7e45251dcf781da71c1644 100644
--- a/runtime/bin/platform_win.cc
+++ b/runtime/bin/platform_win.cc
@@ -5,9 +5,10 @@
 #include "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
+#include "bin/platform.h"
+
 #include "bin/file.h"
 #include "bin/log.h"
-#include "bin/platform.h"
 #include "bin/socket.h"
 #include "bin/utils.h"
 #include "bin/utils_win.h"
@@ -19,6 +20,11 @@ extern bool private_flag_windows_run_tls_destructors;
 
 namespace bin {
 
+const char* Platform::executable_name_ = NULL;
+char* Platform::resolved_executable_name_ = NULL;
+int Platform::script_index_ = 1;
+char** Platform::argv_ = NULL;
+
 bool Platform::Initialize() {
   // Nothing to do on Windows.
   return true;