Work around warnings building with -Wall.

Mark several unused variables as such to avoid triggering build
failures.

Change-Id: Ie9b2b3a375afb7f7b48ccee926312a6fc640bd70
Signed-off-by: Kun Yi <kunyi731@gmail.com>
diff --git a/example.cpp b/example.cpp
index e644f2b..79b9080 100644
--- a/example.cpp
+++ b/example.cpp
@@ -59,7 +59,7 @@
  * This application simply creates an object that registers for incoming value
  * updates for the POST code dbus object.
  */
-int main(int argc, char* argv[])
+int main()
 {
     auto ListenBus = sdbusplus::bus::new_default();
     lpcsnoop::SnoopListen snoop(ListenBus, printPostcode);