[Bug libstdc++/104019] Testsuite 17_intro/headers/c++2020/stdc++_multiple_inclusion.cc failures

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104019

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I have a script that's supposed to pick up those macro inconsistencies, I
wonder why it's not working.

The aliasing violation is real, we should use memset instead.