GN: Makes GN output deterministic

tools/gn/ninja_target_writer.cc

Index: tools/gn/ninja_target_writer.cc
diff --git a/tools/gn/ninja_target_writer.cc b/tools/gn/ninja_target_writer.cc
index 76413076685207938ec73c2bd9d192ae0efa8f16..86bf3f57be6ebfffb28bb0bcfca32e52f224be0b 100644
--- a/tools/gn/ninja_target_writer.cc
+++ b/tools/gn/ninja_target_writer.cc
@@ -17,6 +17,7 @@
 #include "tools/gn/ninja_group_target_writer.h"
 #include "tools/gn/ninja_utils.h"
 #include "tools/gn/output_file.h"
+#include "tools/gn/pointer_set.h"
 #include "tools/gn/scheduler.h"
 #include "tools/gn/string_utils.h"
 #include "tools/gn/substitution_writer.h"
@@ -207,14 +208,13 @@ OutputFile NinjaTargetWriter::WriteInputDepsStampAndGetDep(
   }
 
   // The different souces of input deps may duplicate some targets, so uniquify
-  // them (ordering doesn't matter for this case).
-  std::set<const Target*> unique_deps;
+  // them. Note that the order matters, or the output is non-deterministic.
+  PointerSet<const Target> unique_deps;
 
   // Hard dependencies that are direct or indirect dependencies.
-  const std::set<const Target*>& hard_deps = target_->recursive_hard_deps();
-  for (const auto& dep : hard_deps)
-    unique_deps.insert(dep);
+  const PointerSet<const Target>& hard_deps = target_->recursive_hard_deps();
 
+  unique_deps.insert(hard_deps.begin(), hard_deps.end());
   // Extra hard dependencies passed in.
   unique_deps.insert(extra_hard_deps.begin(), extra_hard_deps.end());