jobs/master-builds: add xgoldmon

Replace the legacy xgoldmon job (not done with jenkins-job-builder) with
a new master-xgoldmon job that works more similar to other master jobs:
- build in docker
- have build commands in a jenkins.sh script

Put the jenkins.sh script into osmo-ci, as the upstream repository is
outside of Osmocom infrastructure.

The motivation for this change is, that the current xgoldmon job is
failing since libosmocore depends on liburing by default. This uncovered
that the job is still running outside of docker, where the dependency
has already been added. The following patches will modernize other jobs
which have the same problem.

Change-Id: Ice5704eb12f3c3a777961bc18a55fac63df80fd6
2 files changed