[Refactor Xcode Objects] Enable generating per file '--help' compiler flag

tools/gn/xcode_writer.cc

 // Copyright 2016 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.
 
 #include "tools/gn/xcode_writer.h"
 
 #include <iomanip>
 #include <map>
 #include <memory>
 #include <sstream>
@@ skipping 335 matching lines @@
   // Sort sources to ensure determinisn of the project file generation and
   // remove duplicate reference to the source files (can happen due to the
   // bundle_data targets).
   std::sort(sources.begin(), sources.end());
   sources.erase(std::unique(sources.begin(), sources.end()), sources.end());
 
   SourceDir source_dir("//");
   for (const SourceFile& source : sources) {
     std::string source_file =
         RebasePath(source.value(), source_dir, absolute_source_path);
-    sources_for_indexing->AddSourceFileToIndexingTarget(source_file,
-                                                        source_file);
+    sources_for_indexing->AddSourceFileToIndexingTarget(
+        source_file, source_file, CompilerFlags::NONE);
   }
 
   projects_.push_back(std::move(sources_for_indexing));
 }
 
 bool XcodeWriter::WriteFiles(const BuildSettings* build_settings, Err* err) {
   for (const auto& project : projects_) {
     if (!WriteProjectFile(build_settings, project.get(), err))
       return false;
   }
@@ skipping 60 matching lines @@
     for (auto* object : pair.second) {
       object->Print(out, 2);
     }
     out << "/* End " << ToString(pair.first) << " section */\n";
   }
 
   out << "\t};\n"
       << "\trootObject = " << project->Reference() << ";\n"
       << "}\n";
 }