Skip Thai character test when libthai is unavailable.

Taken from upstream bug tracker:
https://gitlab.gnome.org/GNOME/pango/merge_requests/161
https://gitlab.gnome.org/GNOME/pango/commit/b73284747ac937e31dc9191f84ed6e24284c88ee

diff --git a/tests/test-break.c b/tests/test-break.c
index 8549b678bba69360d07dce3af21d915412f20d51..47fa3009165e19a331aa04a0df4351ae2323933b 100644
--- a/tests/test-break.c
+++ b/tests/test-break.c
@@ -305,6 +305,12 @@ main (int argc, char *argv[])
       if (!strstr (name, "break"))
         continue;
 
+#ifndef HAVE_LIBTHAI
+      /* four.break involves Thai, so only test it when we have libthai */
+      if (strstr (name, "four.break"))
+        continue;
+#endif
+
       path = g_strdup_printf ("/break/%s", name);
       g_test_add_data_func_full (path, g_test_build_filename (G_TEST_DIST, "breaks", name, NULL),
                                  test_break, g_free);
class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>refs</a><a class='active' href='/guix/log/gnu/packages/pth.scm'>log</a><a href='/guix/tree/gnu/packages/pth.scm?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>tree</a><a href='/guix/commit/gnu/packages/pth.scm?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>commit</a><a href='/guix/diff/gnu/packages/pth.scm?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/packages/pth.scm'>
<input type='hidden' name='id' value='659f790b3fceddca0553da3c7e51480c3bd9519e'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>root</a>/<a href='/guix/log/gnu?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>gnu</a>/<a href='/guix/log/gnu/packages?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>packages</a>/<a href='/guix/log/gnu/packages/pth.scm?id=659f790b3fceddca0553da3c7e51480c3bd9519e'>pth.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/packages/pth.scm?id=659f790b3fceddca0553da3c7e51480c3bd9519e&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2017-03-30 22:59:53 +0200'>2017-03-30</span></td><td><a href='/guix/commit/gnu/packages/pth.scm?id=84157bb8bf2c610584e0836047da4c710f8eaf76'>Merge branch 'master' into core-updates</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2017-03-30 01:30:16 +0200'>2017-03-30</span></td><td><a href='/guix/commit/gnu/packages/pth.scm?id=6fd52309b8f52c9bb59fccffac53e029ce94b698'>gnu: Use HTTPS for almost all gnu.org HOME-PAGEs.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2017-03-02 11:51:43 +0200'>2017-03-02</span></td><td><a href='/guix/commit/gnu/packages/pth.scm?id=10045e5c81b6dfcf3804ceb1bb4b8df04bde7c98'>gnu: pth: Add support for aarch64.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>