Add configurable mount options to overlay

Allows default mount options to be provided through configuration.

Signed-off-by: Derek McGowan <derek@mcg.dev>

snapshots/overlay/plugin/plugin.go

@@ -32,6 +32,9 @@ type Config struct {
 	RootPath      string `toml:"root_path"`
 	UpperdirLabel bool   `toml:"upperdir_label"`
 	SyncRemove    bool   `toml:"sync_remove"`
+
+	// MountOptions are options used for the overlay mount (not used on bind mounts)
+	MountOptions []string `toml:"mount_options"`
 }
 
 func init() {
@@ -60,6 +63,10 @@ func init() {
 				oOpts = append(oOpts, overlay.AsynchronousRemove)
 			}
 
+			if len(config.MountOptions) > 0 {
+				oOpts = append(oOpts, overlay.WithMountOptions(config.MountOptions))
+			}
+
 			ic.Meta.Exports["root"] = root
 			return overlay.NewSnapshotter(root, oOpts...)
 		},