cmd/dist: test cgo internal linking on darwin-arm64

CL 383554 disables testing cgo internal linking on all ARM64 but
Windows, because it doesn't work with newer GCC. But
- darwin-arm64 works, and it does not use GCC
- we don't support cgo internal linking on windows-arm64 anyway.

This CL fixes the condition.

Change-Id: I9eb7b81ef75e482f5e95d2edae4863ba21396432
Reviewed-on: https://go-review.googlesource.com/c/go/+/384269


Trust: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>