Explicitly link runtime against libbpf to fix "DSO missing from command line" error

--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -163,6 +163,7 @@ if(STATIC_LINKING)
   set_property(TARGET LIBELF PROPERTY IMPORTED_LOCATION ${LIBELF_LIBRARIES})
   target_link_libraries(runtime LIBELF)
 else()
+  target_link_libraries(runtime ${LIBBPF_LIBRARIES})
   target_link_libraries(runtime ${LIBELF_LIBRARIES})
 endif(STATIC_LINKING)