[GOLD] Adjust testcase for PowerPC64

[Cary Coutant]

> PowerPC64 needs .got to contain .toc, or at least to have a .toc input
> sections within cooee of the linker created symbol .TOC. in .got.
> OK?
>
>         * testsuite/pr20717.t: Add .got output section containing .toc.

OK, thanks!

I'm curious, though -- since this test doesn't run -- we just link and
check section placement -- does the test actually fail on PPC? If so,
there might still be some issues with orphan section placement. (Maybe
not important ones, as I'd expect most linker scripts to be sane, but
still something I'd want to take a look at.)

-cary