unix: move build constraints comment below copyright message

Make fcntl_linux_32bit.go consistent with all other files in the
package.

Change-Id: If2e21027b0f31ac27d434806c18d9223ee55992f
Reviewed-on: https://go-review.googlesource.com/c/sys/+/261459
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/unix/fcntl_linux_32bit.go b/unix/fcntl_linux_32bit.go
index fc0e50e..8db48e5 100644
--- a/unix/fcntl_linux_32bit.go
+++ b/unix/fcntl_linux_32bit.go
@@ -1,9 +1,9 @@
-// +build linux,386 linux,arm linux,mips linux,mipsle
-
 // Copyright 2014 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 linux,386 linux,arm linux,mips linux,mipsle
+
 package unix
 
 func init() {