Introduce contrib/jenkins.sh to align with other projects
Introduce contrib/jenkins.sh to align with other projects

This change will make jenkins' inline scripts obsolete,
so build testing and gerrit verification jobs [1][2] simply invoke:

  $ ./contrib/jenkins.sh

[1] https://jenkins.osmocom.org/jenkins/view/OsmoTETRA/job/OsmoTETRA/
[2] https://jenkins.osmocom.org/jenkins/view/Jenkins-Gerrit/job/OsmoTETRA-gerrit/

Change-Id: I517e1be8b5680c3cc274fd5ad13ac7c920154e7f

osmocom/osmo-tetra,osmocom/osmo-tetra,osmocom/osmo-tetra