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
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<tr><td><span title='2024-07-20 12:12:15 +0200'>2024-07-20</span></td><td><a href='/guix/commit/gnu/packages/books.scm?id=3518c01cb01452f753b20872c339206c14019065'>gnu: book-sparc: Update to 2.1.0.</a><span class='msg-avail'>...</span></td><td>Artyom V. Poptsov</td></tr>
<tr><td><span title='2024-01-25 21:34:37 +0000'>2024-01-25</span></td><td><a href='/guix/commit/gnu/packages/books.scm?id=9b657bab84be02935d66483da1ebbe4bc78c52fb'>gnu: Sort inputs in (gnu packages books) alphabetically.</a><span class='msg-avail'>...</span></td><td>Sharlatan Hellseher</td></tr>
<tr><td><span title='2024-01-25 21:34:27 +0000'>2024-01-25</span></td><td><a href='/guix/commit/gnu/packages/books.scm?id=d1951037b4cf424058849f122fa54a4c2de83160'>gnu: book-sparc: Update to 2.0.0.</a><span class='msg-avail'>...</span></td><td>Artyom V. Poptsov</td></tr>