runtime: add windows/arm64 cgo-linking code

This code is needed for use with cgo proper
(as opposed to hand-written DLL calls, which
we always use but only exercise cgo execution,
not cgo linking).

Change-Id: Iddc31d9c1c924d83d032b80dca65ddfda6624046
Reviewed-on: https://go-review.googlesource.com/c/go/+/312041


Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>