cmd/dist: test cgo internal linking on darwin-arm64
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 <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
Run-TryBot: Cherry Mui <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>

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