Some build file cleanup

runtime/bin/root_certificates_unsupported.cc

Index: runtime/bin/root_certificates_unsupported.cc
diff --git a/runtime/bin/root_certificates_unsupported.cc b/runtime/bin/root_certificates_unsupported.cc
index 6088e0805bfa9144316889c052332d9d294eb4a0..b1a65f85cfa4d64f01e8e7706775e4862125bfbc 100644
--- a/runtime/bin/root_certificates_unsupported.cc
+++ b/runtime/bin/root_certificates_unsupported.cc
@@ -2,7 +2,10 @@
 // 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)
+
 #include "platform/globals.h"
+#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_ANDROID)
 
 namespace dart {
 namespace bin {
@@ -12,3 +15,7 @@ unsigned int root_certificates_pem_length = 0;
 
 }  // namespace bin
 }  // namespace dart
+
+#endif  // defined(TARGET_OS_MACOS) || defined(TARGET_OS_ANDROID)
+
+#endif  // !defined(DART_IO_SECURE_SOCKET_DISABLED)