clapper-app: Delete temp dir on exit

Pipeline preview creates temp files, so delete whole directory
recursively on app exit. Since these files are used through
launcher/portal with another app, we do not know when user finished
using them, thus we cannot detect and remove them earlier.

src/bin/clapper-app/main.c

@@ -74,5 +74,7 @@ main (gint argc, gchar **argv)
     clapper_app_utils_win_hi_res_clock_stop (resolution);
 #endif
 
+  clapper_app_utils_delete_tmp_dir ();
+
   return status;
 }