unix: add netbsd/arm64 files.

This isn't a real generation, it's mostly a copy of the amd64
files, due to difficulties in generation.

There should be little to no differences between netbsd 64bit
archs.

Change-Id: I1c7b25cfef87220c827018e73695e5ca08987156
GitHub-Last-Rev: 043207b2c25fbfe959e66bddc238d5b2f053a04f
GitHub-Pull-Request: golang/sys#27
Reviewed-on: https://go-review.googlesource.com/c/155738
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

unix/syscall_netbsd_arm64.go

@@ -0,0 +1,33 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build arm64,netbsd
+
+package unix
+
+func setTimespec(sec, nsec int64) Timespec {
+	return Timespec{Sec: sec, Nsec: nsec}
+}
+
+func setTimeval(sec, usec int64) Timeval {
+	return Timeval{Sec: sec, Usec: int32(usec)}
+}
+
+func SetKevent(k *Kevent_t, fd, mode, flags int) {
+	k.Ident = uint64(fd)
+	k.Filter = uint32(mode)
+	k.Flags = uint32(flags)
+}
+
+func (iov *Iovec) SetLen(length int) {
+	iov.Len = uint64(length)
+}
+
+func (msghdr *Msghdr) SetControllen(length int) {
+	msghdr.Controllen = uint32(length)
+}
+
+func (cmsg *Cmsghdr) SetLen(length int) {
+	cmsg.Len = uint32(length)
+}