GN: Don't generate phony rules called "all".

tools/gn/ninja_build_writer.h

Index: tools/gn/ninja_build_writer.h
diff --git a/tools/gn/ninja_build_writer.h b/tools/gn/ninja_build_writer.h
index 6f7bf3813a7090025602230191a38da6787e9b9a..fe7b7a5d3d98f5f95719edf27c481516590841f3 100644
--- a/tools/gn/ninja_build_writer.h
+++ b/tools/gn/ninja_build_writer.h
@@ -6,6 +6,7 @@
 #define TOOLS_GN_NINJA_BUILD_WRITER_H_
 
 #include <iosfwd>
+#include <set>
 #include <vector>
 
 #include "tools/gn/path_output.h"
@@ -44,8 +45,12 @@ class NinjaBuildWriter {
   void WriteSubninjas();
   bool WritePhonyAndAllRules(Err* err);
 
-  void WritePhonyRule(const Target* target, const OutputFile& target_file,
-                      const std::string& phony_name);
+  // Writes a phony rule for the given target with the given name. Adds the new
+  // name to the given set. If the name is already in the set, does nothing.
+  void WritePhonyRule(const Target* target,
+                      const OutputFile& target_file,
+                      const std::string& phony_name,
+                      std::set<std::string>* written_rules);
 
   const BuildSettings* build_settings_;
   std::vector<const Settings*> all_settings_;