* refactor: rtc_clock now defined by variants/*/target modules

examples/simple_secure_chat/main.cpp

@@ -523,7 +523,7 @@ public:
 
 StdRNG fast_rng;
 SimpleMeshTables tables;
-MyMesh the_mesh(radio_driver, fast_rng, *new VolatileRTCClock(), tables);
+MyMesh the_mesh(radio_driver, fast_rng, *new VolatileRTCClock(), tables); // TODO: test with 'rtc_clock' in target.cpp
 
 void halt() {
   while (1) ;