wrc: change -J to -I-

[Mike Hearn]

> The wine internal libraries are still about a megabyte of code, and
> it's silly to duplicate all of that whenever a single function
> changes. Symbol versioning is much better solution to that problem,
> and I don't see much reason for not using it (except on platforms that
> don't support it of course).

Yes, fair enough. I hadn't realised that while libwine is fairly small,
libwine_unicode is huge (not sure what it does, but i expect i'll find
out soon enough).

I don't really have any objection to symvers, other than it does mean
it's harder to eliminate "dead" legacy code. That's only really a
problem if the library changes fairly often though, and even then it's
not such a problem these days.