[Bug c++/115626] relax -Wsign-conversion when initializing from a literal

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115626

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> You can always do `~(cast)0` too.

That is:
__uint128_t t = ~(__uint128_t)0;

does not warn.