Can't have two assemble files

Issue

• I’m playing with OpenShift Enterprise. My aim is to install Jenkins on my project. To do so I use following command:
  oc new-app openshift/jenkins-1-centos7~https://my-stash/openshift-sti-jenkins_ext.git --strategy=source --name=openpaas-jenkins

This command create a new Jenkins instance from the “Jenkins-1-centos7” image. To install specific plugins and so on, I got all the information in my own repository which I mentioned at the end of the command.
This was working but to proceed I also would like to install Maven in my pod. So I created an assemble script to get Maven and unzip it to a directory. But now the whole installation was failing with following error:

2m        2m        1         openpaas-jenkins-1-wwxrl   Pod       spec.containers{openpaas-jenkins}   Failed    {kubelet node1.axadev.enoshift.com}   Failed to start with docker id 6183bc405dd3 with error: API error (500): Cannot start container 6183bc405dd35f64552a0a66b6ee9a33c4369cccc64097851f07db9f2d168aa6: [8] System error: exec format error

It seem I only can have one assemble file in a installation?
How can I install Maven without additional assemble file.