Temporarily patch kardianos/osext to build on FreeBSD

Godeps/_workspace/src/github.com/kardianos/osext/osext_sysctl.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 freebsd openbsd
+// +build darwin openbsd
 
 package osext