[Bug target/88682] new test case c-c++-common/pr51628-10.c fails starting with its introduction in r267313

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88682

--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Yes this does violate aliasing rules.  Easy fix is to add may_alias to the
attributes of unaligned_int128_t.