packager.sh: add '-s' flag to specify ubuntu version and reuse already downloaded dependencies if same repo and branch
packager.sh: add '-s' flag to specify ubuntu version and reuse already downloaded dependencies if same repo and branch


Former-commit-id: 00765f482241d6374cdf0f2ad60421245b30c6fe
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine