virt: add missing #includes

src/basic/virt.c: In function 'detect_vm_device_tree':
src/basic/virt.c:117:17: error: unknown type name '_cleanup_closedir_'
                 _cleanup_closedir_ DIR *dir = NULL;

src/basic/virt.c:128:17: error: implicit declaration of function 'FOREACH_DIRENT' [-Werror=implicit-function-declaration]
                 FOREACH_DIRENT(dent, dir, return -errno)

src/basic/virt.c

@@ -29,6 +29,8 @@
 #include "stat-util.h"
 #include "string-table.h"
 #include "string-util.h"
+#include "fd-util.h"
+#include "dirent-util.h"
 #include "util.h"
 #include "virt.h"