unix: remove Flock syscall for aix

AIX doesn't provide a flock() syscall, it was previously emulated in
package syscall by using fcntl. This emulation was removed in CL 152397.
Since unix.Flock wraps syscall.Flock, the build currently fails on aix
without this change.

Change-Id: Ie887619cd64ae009ea43f00c74e450a5b8f998ac
Reviewed-on: https://go-review.googlesource.com/c/153938
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Clément Chigot <clement.chigot@atos.net>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/example_exec_test.go

@@ -0,0 +1,19 @@
+// Copyright 2018 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 aix darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package unix_test
+
+import (
+	"log"
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+func ExampleExec() {
+	err := unix.Exec("/bin/ls", []string{"ls", "-al"}, os.Environ())
+	log.Fatal(err)
+}

unix/example_flock_test.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package unix_test
 
@@ -13,11 +13,6 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-func ExampleExec() {
-	err := unix.Exec("/bin/ls", []string{"ls", "-al"}, os.Environ())
-	log.Fatal(err)
-}
-
 func ExampleFlock() {
 	f, _ := os.Create("example.lock")
 	if err := unix.Flock(int(f.Fd()), unix.LOCK_EX); err != nil {

unix/syscall_aix.go

@@ -13,10 +13,7 @@
 
 package unix
 
-import (
-	"syscall"
-	"unsafe"
-)
+import "unsafe"
 
 /*
  * Wrapped
@@ -385,10 +382,6 @@ func IoctlGetTermios(fd int, req uint) (*Termios, error) {
 
 //sys	fcntl(fd int, cmd int, arg int) (val int, err error)
 
-func Flock(fd int, how int) (err error) {
-	return syscall.Flock(fd, how)
-}
-
 /*
  * Direct access
  */