DiscoverConnect: add SPP_ENABLED check

Author: ferbar

Diff for: libraries/BluetoothSerial/examples/DiscoverConnect/DiscoverConnect.ino

@@ -22,6 +22,10 @@
 #error Bluetooth is not enabled! Please run `make menuconfig` to and enable it
 #endif
 
+#if !defined(CONFIG_BT_SPP_ENABLED)
+#error Serial Bluetooth not available or not enabled. It is only available for the ESP32 chip.
+#endif
+
 BluetoothSerial SerialBT;