Use to setarrlist to implement UtimesNanoAt with nanosecond precision
(on Mac OS 10.13 with APFS). Translate AT_SYMLINK_NOFOLLOW to
FSOPT_NOFOLLOW correspondingly.

Change-Id: I1468a1f4eecb53b2280ff6329b1ec64e204701f1
Reviewed-on: https://go-review.googlesource.com/75650
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>