cmake HAVE_REGISTER_UPCALL examples

nfs-ganesha/nfs-ganesha src/CMakeLists.txt :890 

check_library_exists(gfapi glfs_upcall_register ${GFAPI_LIBDIR} HAVE_REGISTER_UPCALL)

nfs-ganesha/nfs-ganesha src/CMakeLists.txt :896 

endif(HAVE_REGISTER_UPCALL)