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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<div class='path'>path: <a href='/guix/log/?id=c410e9e531b999546f033d35266f8ac488dee7e0'>root</a>/<a href='/guix/log/gnu?id=c410e9e531b999546f033d35266f8ac488dee7e0'>gnu</a>/<a href='/guix/log/gnu/tests.scm?id=c410e9e531b999546f033d35266f8ac488dee7e0'>tests.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/tests.scm?id=c410e9e531b999546f033d35266f8ac488dee7e0&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-07-25 19:11:36 +0200'>2020-07-25</span></td><td><a href='/guix/commit/gnu/tests.scm?id=a5e2fc73760a2ae023f2e56bdbf8025971f90e64'>utils: Move &lt;location&gt; and '&amp;error-location' to (guix diagnostics).</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/utils.scm (&lt;location&gt;, source-properties-&gt;location)
(location-&gt;source-properties, &amp;error-location): Move to...
* guix/diagnostics.scm: ... here.
* gnu.scm: Adjust imports accordingly.
* gnu/machine.scm: Likewise.
* gnu/system.scm: Likewise.
* gnu/tests.scm: Likewise.
* guix/inferior.scm: Likewise.
* tests/channels.scm: Likewise.
* tests/packages.scm: Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-03-05 16:33:37 +0100'>2020-03-05</span></td><td><a href='/guix/commit/gnu/tests.scm?id=c0b726c2112e0e670dc134583b376541c0a3789a'>tests: Add &lt;system-test&gt; gexp compiler.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/tests.scm (compile-system-test): New gexp compiler.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-01-23 11:26:55 +0100'>2020-01-23</span></td><td><a href='/guix/commit/gnu/tests.scm?id=f79313b3871ebe204c7b29fdb823666af06f48ff'>tests: Fix typo in comment.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/tests.scm: Add missing word in commentary.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-12-18 22:36:37 +0100'>2019-12-18</span></td><td><a href='/guix/commit/gnu/tests.scm?id=ab7010af1f1077c056529769a53a380147c3933f'>gexp: Allow character literals in GEXP-&gt;SEXP.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://bugs.gnu.org/38628&gt;.

* tests/gexp.scm ("lower-gexp, character literal"): New test.
* guix/gexp.scm (gexp-&gt;sexp)[self-quoting?]: Add CHAR? to the tested types.
* guix/repl.scm (self-quoting?): Likewise.
* gnu/tests.scm (marionette-shepherd-service)[self-quoting?]: Likewise.
</span></span></td><td>Marius Bakke</td></tr>