[Bug c/68657] [6 Regression] "gcc -Werror=sign-conversion test.i" shows invalid: -Wsign-conversion is not an option that controls warnings

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68657

--- Comment #5 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Jakub Jelinek from comment #4)
> I run also into issues with -Werror=joined-warn-option=arg
> when testing that, so I've fixed it too.

For the reference, that is PR48088, as far as I can tell.