GN: Don't write duplicate phony rules.

tools/gn/ninja_build_writer.cc

 // 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.
 
 #include "tools/gn/ninja_build_writer.h"
 
 #include <fstream>
+#include <map>
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/path_service.h"
 #include "base/process/process_handle.h"
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/escape.h"
 #include "tools/gn/filesystem_utils.h"
@@ skipping 151 matching lines @@
     path_output_.WriteFile(out_,
                            helper_.GetNinjaFileForToolchain(all_settings_[i]));
     out_ << std::endl;
   }
   out_ << std::endl;
 }
 
 void NinjaBuildWriter::WritePhonyAndAllRules() {
   std::string all_rules;
 
-  // Write phony rules for the default toolchain (don't do other toolchains or
-  // we'll get naming conflicts).
+  // Write phony rules for all uniquely-named targets in the default toolchain.
+  // Don't do other toolchains or we'll get naming conflicts, and if the name
+  // isn't unique, also skip it.
+  std::map<std::string, int> small_name_count;
+  for (size_t i = 0; i < default_toolchain_targets_.size(); i++)
+    small_name_count[default_toolchain_targets_[i]->label().name()]++;
+
   for (size_t i = 0; i < default_toolchain_targets_.size(); i++) {
     const Target* target = default_toolchain_targets_[i];
 
     OutputFile target_file = helper_.GetTargetOutputFile(target);
-    if (target_file.value() != target->label().name()) {
+    if (target_file.value() != target->label().name() &&
+        small_name_count[default_toolchain_targets_[i]->label().name()] == 1) {
       out_ << "build " << target->label().name() << ": phony ";
       path_output_.WriteFile(out_, target_file);
       out_ << std::endl;
     }
 
     if (!all_rules.empty())
       all_rules.append(" $\n    ");
     all_rules.append(target_file.value());
   }
 
   if (!all_rules.empty()) {
     out_ << "\nbuild all: phony " << all_rules << std::endl;
     out_ << "default all" << std::endl;
   }
 }