[dev.link] cmd/link: fix bugs in setArchSyms
[dev.link] cmd/link: fix bugs in setArchSyms

The code in setArchsyms that sets up TOC symbols was buggy; it was
kicking in only for aix-ppc64 and not linux-ppc64. These symbols are
required for both ABIs, so change the guard in question from
"ctx.IsAIX()" to "ctxt.IsPPC64()". Also, the code to create versioned
".TOC." syms was not passing the correct symbol version to the loader
(now fixed).

Change-Id: I356071e528beadad20f61d067059eaf26f06e06b
Reviewed-on: https://go-review.googlesource.com/c/go/+/227257
Run-TryBot: Than McIntosh <4b2922593166fc595a9b1a408f34f5d3817fe9d2@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Jeremy Faller <b3f594e10a9edcf5413cf1190121d45078c62290@golang.org>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

golang/go,nawawi/go,golang/go,CAFxX/go,cloudflare/go,CAFxX/go,CAFxX/go,nawawi/go,nawawi/go,nawawi/go,CAFxX/go,nawawi/go,akutz/go,akutz/go,cloudflare/go,akutz/go,CAFxX/go,cloudflare/go,cloudflare/go,akutz/go,golang/go,cloudflare/go,golang/go,akutz/go,akutz/go,akutz/go,cloudflare/go,nawawi/go,CAFxX/go,cloudflare/go,golang/go,nawawi/go,golang/go,CAFxX/go,akutz/go,golang/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go