syscall: use fchownat(2) in place of lchown(2) for linux/arm64

syscall: use fchownat(2) in place of lchown(2) for linux/arm64

Fixes #11918

Replace calls to lchown(2) with fchownat(2) for linux/arm64 as the former is not suppored.

This change has also landed on the x/sys repo as CL 12837.

Change-Id: I58d4b144e051e36dd650ec9b7f3a02610ea943e5
Reviewed-on: https://go-review.googlesource.com/12833
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dave Cheney <dave@cheney.net>
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Russ Cox <rsc@golang.org>