fix(cxx_indexer): address marked-source differences on builtin functions (#4379)
fix(cxx_indexer): address marked-source differences on builtin functions (#4379)

* fix(cxx_indexer): address marked-source differences on builtin functions

* chore: remove redundant check

kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe,kythe/kythe