Add missing #include for unistd.h

src/shared/symbianutils/virtualserialdevice_posix.cpp

@@ -3,6 +3,7 @@
 #include <errno.h>
 #include <termios.h>
 #include <sys/ioctl.h>
+#include <unistd.h>
 #include <QtCore/QSocketNotifier>
 #include <QtCore/QTimer>
 #include <QtCore/QThread>