message: fb303/cmake: enable RPM generation via cmake
  Summary: Generating RPMs via 'make package' is useful.
diff: @@ -16,6 +16,11 @@ cmake_minimum_required(VERSION 3.8)
  project("fb303" LANGUAGES CXX C)
  +if (NOT DEFINED CPACK_GENERATOR)
  + set(CPACK_GENERATOR "RPM")
  +endif()
  +include(CPack)
  +
  set(CMAKE_CXX_STANDARD 14)
  set(INCLUDE_INSTALL_DIR include CACHE STRING
  