[PATCH] x86_64: Build modf for libc and libm (BZ 33165)

[Florian Weimer]

* H. J. Lu:

> We need to fix:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=33173

That's mostly unrelated to the build/MODULE_NAME issue, though?

Thanks,
Florian