Really remove io support when dart:io is unsupported.

runtime/bin/secure_socket_boringssl.cc

Index: runtime/bin/secure_socket_boringssl.cc
diff --git a/runtime/bin/secure_socket_boringssl.cc b/runtime/bin/secure_socket_boringssl.cc
index 8db4cea34c4be69da22ec80fea21930ff3d45115..530c21a787789977e32a36ec37d44209dbc965fe 100644
--- a/runtime/bin/secure_socket_boringssl.cc
+++ b/runtime/bin/secure_socket_boringssl.cc
@@ -2,7 +2,7 @@
 // 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) || \
@@ -1683,4 +1683,5 @@ int SSLFilter::ProcessWriteEncryptedBuffer(int start, int end) {
 
 #endif  // defined(TARGET_OS_LINUX)
 
-#endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)
+#endif  // !defined(DART_IO_DISABLED) &&
+        // !defined(DART_IO_SECURE_SOCKET_DISABLED)