Really remove io support when dart:io is unsupported.

runtime/bin/secure_socket_boringssl.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_SECURE_SOCKET_DISABLED)
+#if !defined(DART_IO_DISABLED) && !defined(DART_IO_SECURE_SOCKET_DISABLED)
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_ANDROID) || \
     defined(TARGET_OS_LINUX)   || \
     defined(TARGET_OS_WINDOWS)
 
 #include "bin/secure_socket.h"
 #include "bin/secure_socket_boringssl.h"
 
 #include <errno.h>
@@ skipping 1660 matching lines @@
     }
   }
   return bytes_processed;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)
 
-#endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
+#endif  // !defined(DART_IO_DISABLED) &&
+        // !defined(DART_IO_SECURE_SOCKET_DISABLED)