Fix missing CAN bus task enable guard

src/system/can_bus.cpp

@@ -2,6 +2,9 @@
  * @file
  * @brief CAN driver thread.
  */
+#include <sta/config.hpp>
+#ifdef STA_RTOS_CAN_BUS_ENABLE
+
 #include <sta/assert.hpp>
 #include <sta/debug_serial.hpp>
 #include <sta/can/subscribable.hpp>
@@ -406,3 +409,6 @@ extern "C"
 		}
 	}
 }
+
+
+#endif // STA_RTOS_CAN_BUS_ENABLE