build: fix AppArmor compilation

* src/security/virt-aa-helper.c: Add missing include.

src/security/virt-aa-helper.c

@@ -19,6 +19,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <fcntl.h>
 #include <getopt.h>
 #include <stdbool.h>