build_detector.sh: clone into a predictable url

$JUGGLER_DETECTOR_REPOSITORYURL may not be called the same name as $JUGGLER_DETECTOR

Should help with https://github.com/eic/epic/pull/17

requested review from @wdconinc

enabled an automatic merge when the pipeline for 217e32e9 succeeds

aborted the automatic merge because target branch was updated

added 3 commits

• 217e32e9...9bb0f094 - 2 commits from branch master
• 9b884aa4 - build_detector.sh: clone into a predictable url

Compare with previous version

enabled an automatic merge when the pipeline for 9b884aa4 succeeds

merged