Fix cross compile for network and node pkgs

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)

mount/nodes/nodes_unsupported.go

@@ -3,9 +3,11 @@
 package nodes
 
 import (
+	"errors"
+
 	"github.com/docker/libcontainer/devices"
 )
 
 func CreateDeviceNodes(rootfs string, nodesToCreate []*devices.Device) error {
-	return ErrUnsupported
+	return errors.New("Unsupported method")
 }

namespaces/unsupported.go

@@ -3,6 +3,7 @@
 package namespaces
 
 import (
+	"github.com/docker/libcontainer"
 	"github.com/docker/libcontainer/cgroups"
 )
 

network/loopback.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package network
 
 import (

network/netns.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package network
 
 import (

network/network.go

@@ -1,8 +1,11 @@
+// +build linux
+
 package network
 
 import (
-	"github.com/docker/libcontainer/netlink"
 	"net"
+
+	"github.com/docker/libcontainer/netlink"
 )
 
 func InterfaceUp(name string) error {

network/strategy.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package network
 
 import (

network/veth.go

@@ -1,3 +1,5 @@
+// +build linux
+
 package network
 
 import (