Add ability to detect GNU/Hurd when configuring.

Adapted from https://git.hadrons.org/cgit/debian/pkgs/pciutils.git/tree/debian/patches/00-configure-hurd.patch

From e39a3af22501234a91cf28e8c57b45f9379f9101 Mon Sep 17 00:00:00 2001
From: Damien Zammit <damien@zamaudio.com>
Date: Fri, 26 Oct 2018 09:24:04 -0400
Subject: [PATCH 2/2] Add ability to detect GNU/Hurd when configuring

---
 lib/configure |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/lib/configure
+++ b/lib/configure
@@ -25,7 +25,7 @@ if [ -z "$HOST" ] ; then
 		proc=`/usr/sbin/lsdev -C -c processor -S available -F name | head -1`
 		cpu=`/usr/sbin/lsattr -F value -l $proc -a type | sed 's/_.*//'`
 	else
-		cpu=`uname -m | sed 's/^i.86$/i386/;s/^sun4u$/sparc64/;s/^i86pc$/i386/;s/^BePC$/i386/;s/^BeMac$/powerpc/;s/^BeBox$/powerpc/'`
+		cpu=`uname -m | sed 's/^i.86-AT386/i386/;s/^i.86$/i386/;s/^sun4u$/sparc64/;s/^i86pc$/i386/;s/^BePC$/i386/;s/^BeMac$/powerpc/;s/^BeBox$/powerpc/'`
 	fi
 	if [ "$sys" = "DragonFly" ]
 	then
@@ -39,6 +39,10 @@ if [ -z "$HOST" ] ; then
 	then
 		sys=cygwin
 	fi
+	if [ "$sys" = "GNU" ]
+	then
+		sys=gnu
+	fi
 	HOST=${3:-$cpu-$sys}
 fi
 [ -n "$RELEASE" ] && rel="${RELEASE}"
ree/build-aux?id=fcd17fdeac963a0c1a8f8410d061f0b6766aebf4'>tree</a><a href='/guix/commit/build-aux?id=fcd17fdeac963a0c1a8f8410d061f0b6766aebf4'>commit</a><a href='/guix/diff/build-aux?id=fcd17fdeac963a0c1a8f8410d061f0b6766aebf4'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/build-aux'>
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<tr><td><span title='2021-10-17 18:26:44 +0200'>2021-10-17</span></td><td><a href='/guix/commit/build-aux?id=0623138ffa5b066afc25547ffdeb97753cb0ee9a'>maint: Factorize po xref translation.</a><span class='msg-avail'>...<span class='msg-tooltip'>This ensures we use the same method in "make" as in "guix/self.scm".

* Makefile.am: Build guix/build/po.scm.
* build-aux/convert-xref.scm: New file.
* doc/local.mk (xref_command): Use it.
* guix/self.scm (translate-cross-references): Move it...
* guix/build/po.scm: Parse comments and flags separately to find fuzzy
flags.
(translate-cross-references): ...here.
(parse-tree-&gt;assoc): Ignore fuzzy entries.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-06-23 23:35:27 +0200'>2021-06-23</span></td><td><a href='/guix/commit/build-aux?id=ef82ba9dd94369926eb13325d5e7da4306d23dd7'>build: Makefile splits Scheme compilation in four steps.</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://bugs.gnu.org/48963&gt;.
Reported by Julien Lepiller &lt;julien@lepiller.eu&gt;.

This reduces peak memory consumption to something less unreasonable.

* Makefile.am (make-go): Depend on 'make-*-go' targets; remove body.
(guile-compilation-rule): New function.
(MODULES_CORE, MODULES_PACKAGES, MODULES_SYSTEM, MODULES_CLI): New
variables.
&lt;top level&gt;: Call 'guile-compilation-rule' 4 times.
* build-aux/compile-all.scm &lt;top level&gt;: Expect "--total" and
"--processed".  Take them into account when displaying progress
reports.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2021-06-18 14:18:06 +0200'>2021-06-18</span></td><td><a href='/guix/commit/build-aux?id=003728cfab907be5df1411c5faaf466a2b8d5ba2'>build: Remove Guile 2.2 workaround.</a><span class='msg-avail'>...<span class='msg-tooltip'>* build-aux/compile-all.scm &lt;top level&gt;: Remove Guile 2.2 workaround.
</span></span></td><td>Ludovic Courtès</td></tr>