cmd/internal/objabi: enable frame-pointer for iOS arm64
cmd/internal/objabi: enable frame-pointer for iOS arm64

This improves stack unwinding of Go code running on iOS arm64.

Change-Id: I0494f750c15dcb895f9d4a072352f050d731df17
GitHub-Last-Rev: 435a2a1690dad98975f7463f91241831cd73d3df
GitHub-Pull-Request: golang/go#37403
Reviewed-on: https://go-review.googlesource.com/c/go/+/220588
Run-TryBot: Elias Naur <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@eliasnaur.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

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