https://bugs.gentoo.org/854213
--- a/mirdir.c
+++ b/mirdir.c
@@ -88,6 +88,7 @@
 #include <fcntl.h>
 #include <dirent.h>
 #include <time.h>
+#include <unistd.h>
 
 /*
 #include <sys/types.h>