Fixes build with Python >= 3.6:

------
Making all in libgnomeui
make[2]: Entering directory '/tmp/guix-build-libgnomeui-2.24.5.drv-0/libgnomeui-2.24.5/libgnomeui'
  GEN    stamp-gnome-marshal.h
  GEN    stamp-gnometypebuiltins.h
INFO: Reading ./gnome-marshal.list...
  GEN    gnome-marshal.h
Traceback (most recent call last):
  File "/gnu/store/...-glib-2.54.2-bin/bin/glib-mkenums", line 688, in <module>
    process_file(fname)
  File "/gnu/store/...-glib-2.54.2-bin/bin/glib-mkenums", line 420, in process_file
    line = curfile.readline()
  File "/gnu/store/...-python-3.6.3/lib/python3.6/codecs.py", line 321, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xf1 in position 1009: invalid continuation byte
make[2]: *** [Makefile:1109: stamp-gnometypebuiltins.h] Error 1
make[2]: Leaving directory '/tmp/guix-build-libgnomeui-2.24.5.drv-0/libgnomeui-2.24.5/libgnomeui'
make[1]: *** [Makefile:369: all-recursive] Error 1
make[1]: Leaving directory '/tmp/guix-build-libgnomeui-2.24.5.drv-0/libgnomeui-2.24.5'
make: *** [Makefile:296: all] Error 2
------

Patch copied from upstream source repository:

https://git.gnome.org/browse/libgnomeui/commit/?id=30334c28794ef85d8973f4ed0779b5ceed6594f2

From 30334c28794ef85d8973f4ed0779b5ceed6594f2 Mon Sep 17 00:00:00 2001
From: Colin Walters <walters@verbum.org>
Date: Mon, 7 Aug 2017 13:15:26 -0400
Subject: [PATCH] gnome-scores.h: Convert to UTF-8

The new Python `glib-mkenums` barfs on ISO-8859-1 input.
---
 libgnomeui/gnome-scores.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libgnomeui/gnome-scores.h b/libgnomeui/gnome-scores.h
index 911b12d1..4e641d22 100644
--- a/libgnomeui/gnome-scores.h
+++ b/libgnomeui/gnome-scores.h
@@ -27,7 +27,7 @@
  * "High Scores" Widget 
  *
  * AUTHOR: 
- * Horacio J. Peña <horape@compendium.com.ar>
+ * Horacio J. Peña <horape@compendium.com.ar>
  *
  * This is free software (under the terms of the GNU LGPL)
  *
type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=cf0e5934d2209490b97500dcdbf2ba2196d50462'>root</a>/<a href='/guix/log/tests?id=cf0e5934d2209490b97500dcdbf2ba2196d50462'>tests</a>/<a href='/guix/log/tests/store-deduplication.scm?id=cf0e5934d2209490b97500dcdbf2ba2196d50462'>store-deduplication.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/store-deduplication.scm?id=cf0e5934d2209490b97500dcdbf2ba2196d50462&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2024-05-25 16:44:42 +0200'>2024-05-25</span></td><td><a href='/guix/commit/tests/store-deduplication.scm?id=5a7cb59648d102168bd4ecd16f36b69e0f594be1'>deduplication: Detect holes and create sparse files.</a><span class='msg-avail'>...<span class='msg-tooltip'>This reduces disk usage of sparse files that are substituted such as
Guile object files (ELF files).  As of Guile 3.0.9, .go files are sparse
due to ELF sections being aligned on 64 KiB boundaries.

This reduces disk usage reported by “du -sh� by 9% for the ‘guix’
package, by 23% for ‘guile’, and by 35% for ‘guile-git’.

* guix/store/deduplication.scm (hole-size, find-holes): New procedures.
(tee)[seekable?]: New variable.
[read!]: Add case when SEEKABLE? is true.
* tests/store-deduplication.scm (cartesian-product): New procedure.
("copy-file/deduplicate, sparse files (holes: ~a/~a/~a)"): New test set.

Change-Id: Iad2ab7830dcb1220e2026f4a127a6c718afa8964
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2022-12-10 10:56:48 +0100'>2022-12-10</span></td><td><a href='/guix/commit/tests/store-deduplication.scm?id=b129026e2e242e9068158ae6e6fcd8d7c5ea092e'>deduplicate: Use 'sendfile' for small file copies.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/store/deduplication.scm (dump-file/deduplicate): Use 'sendfile'
instead of 'dump-port'.
* tests/store-deduplication.scm ("copy-file/deduplicate, below %deduplication-minimum-size"):
New test.
</span></span></td><td>Ludovic Courtès</td></tr>