tools: Mass fixing of empty prototypes (for -Wstrict-prototypes)

examples/system/ota/advanced_https_ota/main/advanced_https_ota_example.c

@@ -103,7 +103,7 @@ ota_end:
     }
 }
 
-void app_main()
+void app_main(void)
 {
     // Initialize NVS.
     esp_err_t err = nvs_flash_init();