packager: create a new OPT_LIBS_PATH var with the current with the 'opt' PYTHONPATH path
packager: create a new OPT_LIBS_PATH var with the current with the 'opt' PYTHONPATH path

Former-commit-id: bda8065ea501152082e845aceef3731e7c2f8305 [formerly 9a3add13da433826e613149039bb5b2dae40b9f7]
Former-commit-id: 8481a2429a346d20c4e838a5e7ad60f0cd7a6753
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine