See https://bugs.freedesktop.org/show_bug.cgi?id=47792;
should become obsolete with the next release.

diff -u luit-1.1.1.orig/sys.c luit-1.1.1/sys.c
--- luit-1.1.1.orig/sys.c	2012-03-23 05:23:07.000000000 +0100
+++ luit-1.1.1/sys.c	2013-11-27 22:45:53.000000000 +0100
@@ -20,6 +20,8 @@
 THE SOFTWARE.
 */
 
+#define _XOPEN_SOURCE 600
+
 #ifdef HAVE_CONFIG_H
 # include "config.h"
 #endif
>
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<tr><td><span title='2018-12-14 23:32:39 +0100'>2018-12-14</span></td><td><a href='/guix/commit/doc/contributing.texi?id=dc56dc025df0b7ea6915ad1061f8d189d641fe35'>doc: Discourage the use of texlive as input</a><span class='msg-avail'>...</span></td><td>Pierre Neidhardt</td></tr>
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