commit 53bf22e68c36b2fc2281998f8311c7c73c17259c
Author: Érico Rolim <erico.erc@gmail.com>
Date:   Sun Aug 16 15:19:45 2020 -0300

    seek_set.c: add missing header.

diff --git a/src/seek_set.c b/src/seek_set.c
index 19b8265..a1a36d0 100644
--- a/runit-2.1.2/src/seek_set.c
+++ b/runit-2.1.2/src/seek_set.c
@@ -1,6 +1,7 @@
 /* Public domain. */
 
 #include <sys/types.h>
+#include <unistd.h>
 #include "seek.h"
 
 #define SET 0 /* sigh */