style(3p/nix): Reformat project in Google C++ style

Reformatted with:

    fd . -e hh -e cc | xargs clang-format -i

third_party/nix/src/libstore/references.hh

@@ -1,11 +1,11 @@
 #pragma once
 
-#include "types.hh"
 #include "hash.hh"
+#include "types.hh"
 
 namespace nix {
 
-PathSet scanForReferences(const Path & path, const PathSet & refs,
-    HashResult & hash);
-    
+PathSet scanForReferences(const Path& path, const PathSet& refs,
+                          HashResult& hash);
+
 }