Added a missing dependency (libcffi-dev), which is required for thrift build
Added a missing dependency (libcffi-dev), which is required for thrift build

USC-NSL/FlowRadar-P4,p4lang/p4factory,p4lang/p4factory,USC-NSL/FlowRadar-P4,p4lang/p4factory,USC-NSL/FlowRadar-P4,p4lang/p4factory,USC-NSL/FlowRadar-P4,USC-NSL/FlowRadar-P4,p4lang/p4factory,p4lang/p4factory,USC-NSL/FlowRadar-P4