AP_UAVCAN: fixed build of example on px4

libraries/AP_UAVCAN/examples/UAVCAN_sniffer/README.md

@@ -4,12 +4,15 @@ be received by another node.
 
 To build and upload for a Pixhawk style board run this:
 
+```
  ./waf configure --board fmuv3 
  ./waf --target examples/UAVCAN_sniffer --upload
+```
  
 then connect on the USB console. You will see 1Hz packet stats like
 this:
 
+```
 uavcan.equipment.air_data.StaticPressure: 29
 uavcan.equipment.air_data.StaticTemperature: 29
 uavcan.equipment.ahrs.MagneticFieldStrength: 20
@@ -18,6 +21,7 @@ uavcan.equipment.gnss.Fix: 10
 uavcan.equipment.gnss.Auxiliary: 1
 uavcan.equipment.actuator.ArrayCommand: 45
 uavcan.equipment.esc.RawCommand: 368
+```
 
 note that the code requires you to add new msg types you want to
 see. Look for the MSG_CB() and START_CB() macros in the code

libraries/AP_UAVCAN/examples/UAVCAN_sniffer/UAVCAN_sniffer.cpp

@@ -4,7 +4,7 @@
 #include <AP_Common/AP_Common.h>
 #include <AP_HAL/AP_HAL.h>
 
-#if CONFIG_HAL_BOARD == HAL_BOARD_LINUX
+#if CONFIG_HAL_BOARD == HAL_BOARD_CHIBIOS
 
 #include <uavcan/uavcan.hpp>
 
@@ -301,4 +301,17 @@ void loop(void)
 
 AP_HAL_MAIN();
 
+#else
+
+#include <stdio.h>
+
+const AP_HAL::HAL& hal = AP_HAL::get_HAL();
+
+static void loop() { }
+static void setup()
+{
+    printf("Board not currently supported\n");
+}
+
+AP_HAL_MAIN();
 #endif