cmd/link: fix TestRuntimeTypeAttr on ppc64,solaris

For ppc64, skip -linkmode=external per
https://go-review.googlesource.com/c/go/+/106775#message-f95b9bd716e3d9ebb3f47a50492cde9f2972e859

For Solaris, apparently type.* isn't the same as runtime.types. I don't
know why, but runtime.types is what goes into moduledata, and so it's
definitely the more correct thing to use.

Fixes: #24983

Change-Id: I6b465ac7b8f91ce55a63acbd7fe76e4a2dbb6f22
Reviewed-on: https://go-review.googlesource.com/108955


Run-TryBot: Heschi Kreinick <heschi@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>