This patch adds an include needed since icu59:
Source: https://git.archlinux.org/svntogit/community.git/plain/trunk/icu59.patch?h=packages/aegisub
--- aegisub-3.2.2/src/utils.cpp	2014-12-08 02:07:09.000000000 +0200
+++ aegisub-3.2.2/src/utils.cpp	2017-04-26 11:11:15.438239182 +0300
@@ -44,6 +44,7 @@
 #include <boost/filesystem/path.hpp>
 #include <map>
 #include <unicode/locid.h>
+#include <unicode/unistr.h>
 #include <wx/clipbrd.h>
 #include <wx/filedlg.h>
 #include <wx/stdpaths.h>
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<div class='path'>path: <a href='/guix/log/?id=9d95d8bd120072cb3b983da86baa645c5b2ecd89'>root</a>/<a href='/guix/log/etc?id=9d95d8bd120072cb3b983da86baa645c5b2ecd89'>etc</a>/<a href='/guix/log/etc/system-tests.scm?id=9d95d8bd120072cb3b983da86baa645c5b2ecd89'>system-tests.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/etc/system-tests.scm?id=9d95d8bd120072cb3b983da86baa645c5b2ecd89&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-03-05 16:33:38 +0100'>2020-03-05</span></td><td><a href='/guix/commit/etc/system-tests.scm?id=5ec4156bbcaec8337f78411204d59e59e706103b'>tests: Add a manifest for system tests.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>