Fixes Dartium build

runtime/bin/secure_socket_unsupported.cc

Index: runtime/bin/secure_socket_unsupported.cc
diff --git a/runtime/bin/secure_socket_unsupported.cc b/runtime/bin/secure_socket_unsupported.cc
index dc49825e1a87c2eb7d013b5ced06a24bbc5870f1..fb7e713b87e14d4e3681db70aa186b3e37b50027 100644
--- a/runtime/bin/secure_socket_unsupported.cc
+++ b/runtime/bin/secure_socket_unsupported.cc
@@ -11,6 +11,9 @@
 namespace dart {
 namespace bin {
 
+const char* commandline_root_certs_file = NULL;
+const char* commandline_root_certs_cache = NULL;
+
 void FUNCTION_NAME(SecureSocket_Init)(Dart_NativeArguments args) {
   Dart_ThrowException(DartUtils::NewDartArgumentError(
       "Secure Sockets unsupported on this platform"));