net/internal/socktest: build sys_unix.go on AIX

Change-Id: I649fd3714a7729334aa0ec959b20eaa7c6214b5e
Reviewed-on: https://go-review.googlesource.com/59913
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/libgo/go/net/internal/socktest/sys_unix.go b/libgo/go/net/internal/socktest/sys_unix.go
index f983e26..a3d1282 100644
--- a/libgo/go/net/internal/socktest/sys_unix.go
+++ b/libgo/go/net/internal/socktest/sys_unix.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 darwin dragonfly freebsd linux nacl netbsd openbsd solaris
+// +build aix darwin dragonfly freebsd linux nacl netbsd openbsd solaris
 
 package socktest