Linux: change protobuf default option to allow building

sync/protocol/nigori_specifics.proto

 // Copyright (c) 2012 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.
 //
 // Sync protocol datatype extension for nigori keys.
 
 // Update proto_value_conversions{.h,.cc,_unittest.cc} if you change
 // any fields in this file.
 
 syntax = "proto2";
 
-option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
-
 package sync_pb;
 
 import "encryption.proto";
 
 message NigoriKey {
   optional string name = 1;
   optional bytes user_key = 2;
   optional bytes encryption_key = 3;
   optional bytes mac_key = 4;
 }
@@ skipping 80 matching lines @@
   // The time (in epoch milliseconds) at which the keystore migration was
   // performed.
   optional int64 keystore_migration_time = 32;
 
   // The time (in epoch milliseconds) at which a custom passphrase was set.
   // Note: this field may not be set if the custom passphrase was applied before
   // this field was introduced.
   optional int64 custom_passphrase_time = 33;
 }