[Bug lto/58905] Undefined symbol not report when compile with -flto -O1

[npickito at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58905
--- Comment #2 from Kito Cheng <npickito at gmail dot com> ---
However older version autoconf use such style to detect,

It will broken some older project when configure with lto.