How do I conditionally map a directory with Maven RPM plugin?

Question

I have written a master parent pom for use with multiple projects.

In this pom we have setup the RPM plugin to package things. I am starting to create a new standard where we want a new top level folder to exist in every repo.

The problem is I need to not fail to create an RPM if the directory does not exist, at least for now.

I have added a mapping like so

<mapping>
  <directory>/var/lib/appName/${service}/deploy</directory>
  <filemode>775</filemode>
  <username>${serviceuser}</username>
  <groupname>${servicegroup}</groupname>
  <sources>
    <source>
      <location>deploy</location>
    </source>
  </sources>
</mapping>

The build fails when the folder does not exist.

The error is

Failed to execute goal org.codehaus.mojo:rpm-maven-plugin:2.1-alpha-4:attached-rpm (default) on project example-service: Source location deploy does not exist -> [Help 1]