[Benchmarks] add missing links to libdl

benchmark/CMakeLists.txt

@@ -47,6 +47,7 @@ IF(CPPADCG_FOUND)
   ADD_BENCH(timings-cg TRUE)
   SET_PROPERTY(TARGET timings-cg PROPERTY CXX_STANDARD 11)
   PKG_CONFIG_USE_DEPENDENCY(timings-cg "cppadcg")
+  TARGET_LINK_LIBRARIES(timings-cg ${CMAKE_DL_LIBS})
 ENDIF(CPPADCG_FOUND)
 
 # timings
@@ -74,5 +75,3 @@ ADD_BENCH(timings-eigen)
 IF(URDFDOM_FOUND AND HPP_FCL_FOUND)
   ADD_BENCH(timings-geometry TRUE)
 ENDIF(URDFDOM_FOUND AND HPP_FCL_FOUND)
-
-