See http://lists.gnu.org/archive/html/bug-gnulib/2009-10/msg00089.html .

From dd0ebefe4fe761f6f422a400430db53c64dbffd7 Mon Sep 17 00:00:00 2001
From: Eric Blake <ebb9@byu.net>
Date: Tue, 6 Oct 2009 20:44:13 -0600
Subject: [PATCH] getopt: fix compilation on darwin
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* lib/getopt.in.h (includes): Leave breadcrumbs during system
include.
* lib/unistd.in.h (getopt): Use them to avoid recursive include.
Reported by Ludovic Courtès.

Signed-off-by: Eric Blake <ebb9@byu.net>
---
 ChangeLog       |    5 +++++
 lib/getopt.in.h |    6 +++++-
 lib/unistd.in.h |    2 +-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/lib/getopt.in.h b/lib/getopt.in.h
index 9de467a..7377f3c 100644
--- a/lib/getopt.in.h
+++ b/lib/getopt.in.h
@@ -22,9 +22,13 @@
 @PRAGMA_SYSTEM_HEADER@
 #endif

-/* The include_next requires a split double-inclusion guard.  */
+/* The include_next requires a split double-inclusion guard.  We must
+   also inform the replacement unistd.h to not recursively use
+   <getopt.h>; our definitions will be present soon enough.  */
 #if @HAVE_GETOPT_H@
+# define _GL_SYSTEM_GETOPT
 # @INCLUDE_NEXT@ @NEXT_GETOPT_H@
+# undef _GL_SYSTEM_GETOPT
 #endif

 #ifndef _GL_GETOPT_H
diff --git a/lib/unistd.in.h b/lib/unistd.in.h
index 38e2e13..b6ea889 100644
--- a/lib/unistd.in.h
+++ b/lib/unistd.in.h
@@ -49,7 +49,7 @@
 #endif

 /* Get getopt(), optarg, optind, opterr, optopt.  */
-#if @GNULIB_UNISTD_H_GETOPT@
+#if @GNULIB_UNISTD_H_GETOPT@ && !defined _GL_SYSTEM_GETOPT
 # include <getopt.h>
 #endif