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
'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=7c8f3dfa34bf644066035a352ddf8f5191b3ec80'>refs</a><a class='active' href='/guix/log/CODE-OF-CONDUCT'>log</a><a href='/guix/tree/CODE-OF-CONDUCT?id=7c8f3dfa34bf644066035a352ddf8f5191b3ec80'>tree</a><a href='/guix/commit/CODE-OF-CONDUCT?id=7c8f3dfa34bf644066035a352ddf8f5191b3ec80'>commit</a><a href='/guix/diff/CODE-OF-CONDUCT?id=7c8f3dfa34bf644066035a352ddf8f5191b3ec80'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/CODE-OF-CONDUCT'>
<input type='hidden' name='id' value='7c8f3dfa34bf644066035a352ddf8f5191b3ec80'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=7c8f3dfa34bf644066035a352ddf8f5191b3ec80'>root</a>/<a href='/guix/log/CODE-OF-CONDUCT?id=7c8f3dfa34bf644066035a352ddf8f5191b3ec80'>CODE-OF-CONDUCT</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/CODE-OF-CONDUCT?id=7c8f3dfa34bf644066035a352ddf8f5191b3ec80&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-03-01 13:18:01 -0500'>2022-03-01</span></td><td><a href='/guix/commit/CODE-OF-CONDUCT?id=c67912011154e2b347cdf6f3e633e87fd44f409c'>CODE-OF-CONDUCT: Add a top notice.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2022-03-01 13:07:04 -0500'>2022-03-01</span></td><td><a href='/guix/commit/CODE-OF-CONDUCT?id=4254d74b4ca6d4aa78b7fa055fc9ec72a2e93ad3'>CODE-OF-CONDUCT: Update to version 2.1.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>