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..8cd8573786ef282996ce6b323303ae5c94f81fdb 100644
--- a/tools/gn/ninja_target_writer.cc
+++ b/tools/gn/ninja_target_writer.cc
@@ -8,6 +8,7 @@
 
 #include "base/files/file_util.h"
 #include "base/strings/string_util.h"
+#include "tools/gn/dereference_comparator.h"
 #include "tools/gn/err.h"
 #include "tools/gn/escape.h"
 #include "tools/gn/filesystem_utils.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());