Fix OSX compilation for aufs

graphdriver/aufs/aufs.go

@@ -30,7 +30,6 @@ import (
 	"os/exec"
 	"path"
 	"strings"
-	"syscall"
 )
 
 func init() {
@@ -327,7 +326,7 @@ func (a *Driver) aufsMount(ro []string, rw, target string) (err error) {
 
 		for _, layer := range ro {
 			branch := fmt.Sprintf("append:%s=ro+wh", layer)
-			if err = mount("none", target, "aufs", syscall.MS_REMOUNT, branch); err != nil {
+			if err = mount("none", target, "aufs", MsRemount, branch); err != nil {
 				return
 			}
 		}

graphdriver/aufs/mount_darwin.go

@@ -2,6 +2,8 @@ package aufs
 
 import "errors"
 
+const MsRemount = 0
+
 func mount(source string, target string, fstype string, flags uintptr, data string) (err error) {
 	return errors.New("mount is not implemented on darwin")
 }

graphdriver/aufs/mount_linux.go

@@ -2,6 +2,8 @@ package aufs
 
 import "syscall"
 
+const MsRemount = syscall.MS_REMOUNT
+
 func mount(source string, target string, fstype string, flags uintptr, data string) error {
 	return syscall.Mount(source, target, fstype, flags, data)
 }