Linux: enabled commander module

The commander module now compiles for Linux.

state_machine_helper_linux.cpp iterates over the virtual devices vs
all devices under /dev as per NuttX when disabling publishing.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/modules/commander/airspeed_calibration.cpp

@@ -41,6 +41,7 @@
 #include "commander_helper.h"
 
 #include <stdio.h>
+#include <unistd.h>
 #include <fcntl.h>
 #include <poll.h>
 #include <math.h>