unix: use setattrlist for UtimesNano on Darwin for ns resolution

Follow CL 74952 for x/sys/unix.

Update golang/go#22528

Change-Id: Id146da75b80a64cfa4eac28e9bb7b3befe944718
Reviewed-on: https://go-review.googlesource.com/75610
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

unix/syscall_darwin.go

@@ -187,6 +187,35 @@ func Getfsstat(buf []Statfs_t, flags int) (n int, err error) {
 	return
 }
 
+func setattrlistTimes(path string, times []Timespec) error {
+	_p0, err := BytePtrFromString(path)
+	if err != nil {
+		return err
+	}
+
+	var attrList attrList
+	attrList.bitmapCount = ATTR_BIT_MAP_COUNT
+	attrList.CommonAttr = ATTR_CMN_MODTIME | ATTR_CMN_ACCTIME
+
+	// order is mtime, atime: the opposite of Chtimes
+	attributes := [2]Timespec{times[1], times[0]}
+
+	const options = 0
+	_, _, e1 := Syscall6(
+		SYS_SETATTRLIST,
+		uintptr(unsafe.Pointer(_p0)),
+		uintptr(unsafe.Pointer(&attrList)),
+		uintptr(unsafe.Pointer(&attributes)),
+		uintptr(unsafe.Sizeof(attributes)),
+		uintptr(options),
+		0,
+	)
+	if e1 != 0 {
+		return e1
+	}
+	return nil
+}
+
 func utimensat(dirfd int, path string, times *[2]Timespec, flags int) error {
 	// Darwin doesn't support SYS_UTIMENSAT
 	return ENOSYS