Make it work on opensolaris

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/log.c b/log.c
index 8f92e93..191f806 100644
--- a/log.c
+++ b/log.c
@@ -4,6 +4,7 @@
  */
 #include <stdio.h>
 #include <stdlib.h>
+#include <libgen.h>
 #include <assert.h>
 #include "list.h"
 #include "fio.h"