[Bug sanitizer/66308] -fsanitize=alignment is missing "downcast of misaligned address" checks

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66308

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Only the upcast is really a bug.  Downcasting is not a problem here.