Add chrome crash service to GN build on Windows.

build/buildflag_header.gni

 # Copyright 2015 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.
 
 # Generates a header with preprocessor defines specified by the build file.
 # The GYP version of this (with instructions) is build/buildflag_header.gypi.
 #
 # The flags are converted to function-style defines with mangled names and
 # code uses an accessor macro to access the values. This is to try to
 # minimize bugs where code checks whether something is defined or not, and
@@ skipping 104 matching lines @@
     if (defined(invoker.flags)) {
       response_file_contents += invoker.flags
     }
 
     args = [
       "--output",
       header_file,  # Not rebased, Python script puts it inside gen-dir.
       "--rulename",
       get_label_info(":$target_name", "label_no_toolchain"),
       "--gen-dir",
-      rebase_path(root_gen_dir, root_out_dir),
+      rebase_path(root_gen_dir, root_build_dir),
       "--definitions",
       "{{response_file_name}}",
     ]
 
     forward_variables_from(invoker,
                            [
                              "deps",
                              "public_deps",
                              "testonly",
                              "visibility",
                            ])
   }
 }