[Bug c++/78551] [5/6/7 Regression] Internal compiler error with constexpr initialization of union

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78551

--- Comment #11 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
Created attachment 40276
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40276&action=edit
non-union crash

Union is not necessary to trigger the ICE.  All we need is to initialize a char
array with a string constant, and then try and write an element of the array.