Add extra_repo_url in image building jobs

Change-Id: I7729bbb9fe0606dbcee259593a6f05c9698cf7b4
diff --git a/jenkins/client/job/docker/build-images.yml b/jenkins/client/job/docker/build-images.yml
index ca1d058..0f2cdc9 100644
--- a/jenkins/client/job/docker/build-images.yml
+++ b/jenkins/client/job/docker/build-images.yml
@@ -54,3 +54,6 @@
               DOCKER_GIT_TAG:
                 type: boolean
                 default: "true"
+              EXTRA_REPO_URL:
+                type: string
+                default: "${_param:jenkins_aptly_url}"