[Bug lto/66784] no symbol emitted for builtin with lto

[guido.hatzsis at yandex dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66784

--- Comment #2 from Guido Haztsis <guido.hatzsis at yandex dot com> ---
Well I believe that the is_builtin_fn cometh from here:

+2488 gcc/lto-streamer-out.c 
   if (!TREE_PUBLIC (t)
       || is_builtin_fn (t)
       || DECL_ABSTRACT_P (t)
       || (TREE_CODE (t) == VAR_DECL && DECL_HARD_REGISTER (t)))