Workaround for PATH_MAX usage on the Hurd.

Taken from https://salsa.debian.org/debian/screen/-/blob/master/debian/patches/61-default-PATH_MAX-if-undefined-for-hurd.patch

Description: Set PATH_MAX to 4096 if undefined
 Fixes FTBFS since 4.4.0 on GNU/Hurd. Updated to add one more occurrence for 4.5.0.
Author: Axel Beckert <abe@debian.org>
Bug: https://savannah.gnu.org/bugs/?50089
Last-Updated: 2017-01-18

--- a/tty.sh
+++ b/tty.sh
@@ -1478,6 +1478,13 @@
   return 0;
 }
 
+/*
+ * Define PATH_MAX to 4096 if it's not defined, like on GNU/Hurd
+ */
+
+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
 
 int CheckTtyname (char *tty)
 {
--- a/screen.h
+++ b/screen.h
@@ -109,6 +109,13 @@
 # define DEFAULT_BUFFERFILE	"/tmp/screen-exchange"
 #endif
 
+/*
+ * Define PATH_MAX to 4096 if it's not defined, like on GNU/Hurd
+ */
+
+#ifndef PATH_MAX
+#define PATH_MAX 4096
+#endif
 
 #if defined(hpux) && !(defined(VSUSP) && defined(VDSUSP) && defined(VWERASE) && defined(VLNEXT))
 # define HPUX_LTCHARS_HACK
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<div class='path'>path: <a href='/guix/log/?id=7d5f0227d679a3650f24cbdf37905a13d039e951'>root</a>/<a href='/guix/log/tests?id=7d5f0227d679a3650f24cbdf37905a13d039e951'>tests</a>/<a href='/guix/log/tests/services?id=7d5f0227d679a3650f24cbdf37905a13d039e951'>services</a>/<a href='/guix/log/tests/services/linux.scm?id=7d5f0227d679a3650f24cbdf37905a13d039e951'>linux.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/tests/services/linux.scm?id=7d5f0227d679a3650f24cbdf37905a13d039e951&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-08-02 15:54:37 +0300'>2020-08-02</span></td><td><a href='/guix/commit/tests/services/linux.scm?id=587e0d911dfff81647015e89847084b606e68f71'>services: Add zram-device-service.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/linux.scm (&lt;zram-device-configuration&gt;): New record.
(zram-device-service-type): New variable.
* doc/guix.texi (Linux Services): Document it.
* tests/services/linux.scm (zram-swap-device-test): New tests.
</span></span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2020-01-31 23:37:13 -0500'>2020-01-31</span></td><td><a href='/guix/commit/tests/services/linux.scm?id=d3e439e355284f136ff13eb3e6fffb4661552f3b'>gnu: Add earlyoom-service-type.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/services/linux.scm: New file.
* tests/services/linux.scm: Add test.
* Makefile.am (SCM_TESTS): Register test.
* doc/guix.texi (Linux Services): Add a new section and document the new
service and its configuration.
</span></span></td><td>Maxim Cournoyer</td></tr>