Fix fuzzer build to also use fake clock

tests/fuzz/CMakeLists.txt

@@ -52,7 +52,7 @@ list(APPEND LIBS "${open62541_LIBRARIES}")
 
 # Use different plugins for testing
 set(fuzzing_plugin_sources ${PROJECT_SOURCE_DIR}/plugins/ua_network_tcp.c
-        ${PROJECT_SOURCE_DIR}/plugins/ua_clock.c
+        ${PROJECT_SOURCE_DIR}/tests/testing-plugins/testing_clock.c
         ${PROJECT_SOURCE_DIR}/tests/testing-plugins/testing_networklayers.c
         ${PROJECT_SOURCE_DIR}/plugins/ua_log_stdout.c
         ${PROJECT_SOURCE_DIR}/plugins/ua_config_default.c