PR pending / bug #906004
https://github.com/filebench/filebench/pull/160.patch
From bee9657493f66432a20d1e9e02132da5819b6133 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Tue, 20 Dec 2022 10:11:08 +0100
Subject: [PATCH] configure.ac: Improve C99 compatibility of HAVE_IOPRIO check

Include <unistd.h> to obtain a declaration of the syscall function.
Implicit function declarations are likely to be rejected by future
compilers by default.
--- a/configure.ac
+++ b/configure.ac
@@ -370,7 +370,8 @@ AC_TRY_COMPILE([
 # check for I/O priority system calls
 AC_MSG_CHECKING(for I/O priority system calls)
 AC_TRY_COMPILE([
-	#include <syscall.h>],
+	#include <syscall.h>
+	#include <unistd.h>],
   	[(void)syscall(__NR_ioprio_set, 0, 0, 0);
 	],[
 	    AC_DEFINE(HAVE_IOPRIO, 1, [ Define if you have I/O priority syscalls. ])