Minimally patch libtheora's ancient config.guess to support mips64.

--- libtheora/config.guess.orig	2009-02-23 22:50:50.000000000 -0500
+++ libtheora/config.guess	2013-10-31 23:49:48.155999944 -0400
@@ -798,25 +798,24 @@
     m68*:Linux:*:*)
 	echo ${UNAME_MACHINE}-unknown-linux-gnu
 	exit 0 ;;
-    mips:Linux:*:*)
+    mips:Linux:*:* | mips64:Linux:*:*)
 	eval $set_cc_for_build
 	sed 's/^	//' << EOF >$dummy.c
 	#undef CPU
-	#undef mips
-	#undef mipsel
+	#undef ${UNAME_MACHINE}
+	#undef ${UNAME_MACHINE}el
 	#if defined(__MIPSEL__) || defined(__MIPSEL) || defined(_MIPSEL) || defined(MIPSEL)
-	CPU=mipsel
+	CPU=${UNAME_MACHINE}el
 	#else
 	#if defined(__MIPSEB__) || defined(__MIPSEB) || defined(_MIPSEB) || defined(MIPSEB)
-	CPU=mips
+	CPU=${UNAME_MACHINE}
 	#else
 	CPU=
 	#endif
 	#endif
 EOF
-	eval `$CC_FOR_BUILD -E $dummy.c 2>/dev/null | grep ^CPU=`
-	rm -f $dummy.c && rmdir $tmpdir
-	test x"${CPU}" != x && echo "${CPU}-pc-linux-gnu" && exit 0
+	eval `$CC_FOR_BUILD -E $dummy.c 2>/dev/null | grep '^CPU'`
+	test x"${CPU}" != x && { echo "${CPU}-unknown-linux-gnu"; exit 0; }
 	;;
     ppc:Linux:*:*)
 	echo powerpc-unknown-linux-gnu
 class='active' href='/guix/log/gnu/machine.scm'>log</a><a href='/guix/tree/gnu/machine.scm?id=2a2da78326e80dabba2d02afa790f487e85df3e4'>tree</a><a href='/guix/commit/gnu/machine.scm?id=2a2da78326e80dabba2d02afa790f487e85df3e4'>commit</a><a href='/guix/diff/gnu/machine.scm?id=2a2da78326e80dabba2d02afa790f487e85df3e4'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/machine.scm'>
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<div class='path'>path: <a href='/guix/log/?id=2a2da78326e80dabba2d02afa790f487e85df3e4'>root</a>/<a href='/guix/log/gnu?id=2a2da78326e80dabba2d02afa790f487e85df3e4'>gnu</a>/<a href='/guix/log/gnu/machine.scm?id=2a2da78326e80dabba2d02afa790f487e85df3e4'>machine.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/machine.scm?id=2a2da78326e80dabba2d02afa790f487e85df3e4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-12-08 00:47:26 +0100'>2019-12-08</span></td><td><a href='/guix/commit/gnu/machine.scm?id=a1d7920861a8d6c6774149eaf939eb2636942090'>machine: Remove unnecessary record self-referencing bindings.</a><span class='msg-avail'>...<span class='msg-tooltip'>'this-machine' and 'this-machine-ssh-configuration' were useless given
that there are no thunked fields.

* gnu/machine.scm (&lt;machine&gt;)[this-machine]: Remove.
* gnu/machine/ssh.scm (&lt;machine-ssh-configuration&gt;)
[this-machine-ssh-configuration]: Remove.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-12-07 00:59:56 +0100'>2019-12-07</span></td><td><a href='/guix/commit/gnu/machine.scm?id=eaabc5e87f4e48d7bce88ca231f5fc2d554ca3d6'>machine: Add provenance tracking to each machine operating system.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine.scm (&lt;machine&gt;): Rename accessor to
'%machine-operating-system'.
(machine-operating-system): New procedure.
* doc/guix.texi (Service Reference): Mention it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-08-15 07:43:09 -0400'>2019-08-15</span></td><td><a href='/guix/commit/gnu/machine.scm?id=9c70c460a05b2bc60f3f3602f0a2dba0f79ce86c'>machine: Implement 'roll-back-machine'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine.scm (roll-back-machine, &amp;deploy-error, deploy-error?)
(deploy-error-should-roll-back)
(deploy-error-captured-args): New variable.
* gnu/machine/ssh.scm (roll-back-managed-host): New variable.
* guix/scripts/deploy.scm (guix-deploy): Roll-back systems when a
deployment fails.
</span></span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-08-06 15:48:51 -0400'>2019-08-06</span></td><td><a href='/guix/commit/gnu/machine.scm?id=d97ce20400b5d2967bfbc0e9fbfb99bbb2daed4f'>machine: Rename 'system' field.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine.scm (machine-system): Delete variable.
(machine-operating-system): New variable.
All callers changed.
* doc/guix.texi (Invoking guix deploy): Use the
'machine-operating-system' accessor rather than 'machine-system'.
</span></span></td><td>Jakob L. Kreuze</td></tr>
<tr><td><span title='2019-07-06 02:10:04 -0400'>2019-07-06</span></td><td><a href='/guix/commit/gnu/machine.scm?id=fa9edf09e992db7510c7471486dffc93e1e707e5'>gnu: Add machine type for deployment specifications.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/machine.scm: New file.
* gnu/machine/ssh.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
</span></span></td><td>Jakob L. Kreuze</td></tr>