allow setting default node name for companion via build flag

examples/companion_radio/main.cpp

@@ -863,6 +863,11 @@ public:
     mesh::Utils::toHex(pub_key_hex, self_id.pub_key, 4);
     strcpy(_prefs.node_name, pub_key_hex);
 
+    // if name is provided as a build flag, use that as default node name instead
+    #ifdef ADVERT_NAME
+    strcpy(_prefs.node_name, ADVERT_NAME);
+    #endif
+
     // load persisted prefs
     if (_fs->exists("/new_prefs")) {
       loadPrefsInt("/new_prefs");   // new filename