[Bug other/105335] libiberty does not handle script exit codes correctly.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105335

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The reason for the lower byte only is because posix says exit value is
truncated to char.
This seems like libiberty not knowing that win32 does not truncate to byte
unlike posix.

Note I thought the c standard says the same too.