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

[jakub at gcc dot gnu.org]

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

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jakub at gcc dot gnu.org

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 36913
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36913&action=edit
gcc6-pr68657.patch

Untested fix.  I run also into issues with -Werror=joined-warn-option=arg
when testing that, so I've fixed it too.
Haven't touched java.opt, because all the warning options in there are ignored
(unless jc1 takes them from the driver).