[Bug c++/113919] Nested anonymous unions should be prohibited in ISO C++

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113919

--- Comment #3 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
clang++ has -Wnested-anon-types so I think we need that too.