all: go fmt ./...

Make all our package sources use Go 1.17 gofmt format
(adding //go:build lines).

Not strictly necessary but will avoid spurious changes
as files are edited.

Part of //go:build change (#41184).
See https://golang.org/design/draft-gobuild

Change-Id: I01667f826428426a39c84717d02efa25fa44553c
Reviewed-on: https://go-review.googlesource.com/c/sys/+/294490
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matt Layher <mdlayher@gmail.com>
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Russ Cox <rsc@golang.org>

unix/zsyscall_darwin_arm64.go

@@ -1,6 +1,7 @@
 // go run mksyscall.go -tags darwin,arm64,go1.12 syscall_bsd.go syscall_darwin.go syscall_darwin_arm64.go
 // Code generated by the command above; see README.md. DO NOT EDIT.
 
+//go:build darwin && arm64 && go1.12
 // +build darwin,arm64,go1.12
 
 package unix