GN: Work on Linux build defines

build/config/crypto.gni

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # This file declares build flags for the SSL library configuration.
+#
+# TODO(brettw) this should probably be moved to src/crypto or somewhere, and
+# the global build dependency on it should be removed.
 
 declare_args() {
   # Use OpenSSL instead of NSS. This is used for Android and is experimental
   # in other cases (see http://crbug.com/62803).
   use_openssl = false
 }
 
 if (is_linux && !use_openssl) {
   use_nss = true
 } else {
   use_nss = false
 }