Fix compile error due to missing ENOMEM on some platforms

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/helpers.c b/helpers.c
index ba5c654..21b9913 100644
--- a/helpers.c
+++ b/helpers.c
@@ -1,5 +1,6 @@
 #include <malloc.h>
 #include <stdlib.h>
+#include <errno.h>
 
 #include "compiler/compiler.h"