[Bug ipa/94293] [missed optimization] Useless statements populating local string not removed

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94293

--- Comment #11 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
In fact doing:
```
#include <bits/c++config.h>
#undef _GLIBCXX_EXTERN_TEMPLATE
```

Fixes the code on the trunk so yes this is basically a dup of bug 86590 now.