[hackers] [sbase] Fix usage for printf(1) || sin

[git]

commit ccf0fbcd7b7e3c9eaa86524bf1c4049da72b945f
Author: sin <s...@2f30.org>
Date:   Fri Apr 3 10:41:38 2015 +0100

    Fix usage for printf(1)

diff --git a/printf.c b/printf.c
index 13ba21e..8c204b8 100644
--- a/printf.c
+++ b/printf.c
@@ -11,7 +11,7 @@
 static void
 usage(void)
 {
-       eprintf("%s format [arg ...]\n", argv0);
+       eprintf("usage: %s format [arg ...]\n", argv0);
 }
 
 int