[Bug testsuite/78529] gcc.c-torture/execute/builtins/strcat-chk.c failed with lto/O2

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78529

--- Comment #44 from Wilco <wilco at gcc dot gnu.org> ---
Backported fix to all active branches so this should never fail again.