test: file-descriptor: Fix undefined O_TMPFILE compilation error

O_TMPFILE is not defined by all libc implementations. libcamera has an
internal definition in utils.h to work around this. Include utils.h in
the test to fix the compilation error.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

test/file-descriptor.cpp

@@ -14,6 +14,7 @@
 #include <libcamera/file_descriptor.h>
 
 #include "test.h"
+#include "utils.h"
 
 using namespace libcamera;
 using namespace std;