[Bug c/66826] Unused result from dlsym in constructor results in a segfault

[quae at daurnimator dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66826

--- Comment #1 from Daurnimator <quae at daurnimator dot com> ---
nalaginrut (from #gcc irc channel) confirmed that the issue only occurs in GCC
5 at -O2 and higher. (the bug is *not* present in GCC 4.9 or at -O1).

Note: only the compilation of shared.so matters (the main binary can be
compiled with any setting or compiler and the same behaviour is shown.)