usage.c: remove reference to busybox.h
*: s/include "busybox.h"/include "libbb.h"

diff --git a/runit/sv.c b/runit/sv.c
index 01488c0..a918bb7 100644
--- a/runit/sv.c
+++ b/runit/sv.c
@@ -153,7 +153,7 @@
 
 #include <sys/poll.h>
 #include <sys/file.h>
-#include "busybox.h"
+#include "libbb.h"
 #include "runit_lib.h"
 
 static const char *acts;