Correctly get processors online.

Index: args.c
--- args.c.orig
+++ args.c
@@ -25,14 +25,15 @@
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
-#include <error.h>
+#include <unistd.h>
 #include <gelf.h>
-#include <sys/sysinfo.h>
 
 #include "args.h"
 
 #include "util.h"
 
+extern void error(int, int, const char *, ...);
+
 #if DEVEL
 int tracing;
 int ignore_size;
@@ -735,7 +736,7 @@ parse_args (int argc, char *argv[], bool *hardlink, co
 
   if (max_forks == -1)
     {
-      long nprocs = get_nprocs ();
+      long nprocs = sysconf(_SC_NPROCESSORS_ONLN);
       /* Be conservative on max forks: 4 procs may be actually be 4 SMT
 	 threads with only 2 cores.  */
       max_forks = nprocs / 2;