packager.sh: moved build_root under <ubuver> base directory
packager.sh: moved build_root under <ubuver> base directory


Former-commit-id: 612847bda650abf3d12a99be4c69c45123bb93a8 [formerly be53c0353b6cfa837551f2f6014b54637ba51c7e]
Former-commit-id: fa41795a94cfc31756a58e15c91a992876a58768
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine