Ensure junit is created in failed tarball and out-of-tree jobs

Failed system:gcc:tarball after script:

    Running after script...
    $ (source bin/tests/system/conf.sh; $PYTHON bin/tests/convert-trs-to-junit.py . > junit.xml)
    /bin/bash: line 159: bin/tests/system/conf.sh: No such file or directory
66 jobs for !6465 with mnowak/create-junit-for-failed-tarball-and-out-of-tree-jobs in 17 minutes and 31 seconds (queued for 6 seconds)
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