Make weasyprint load dynamic libraries from hard-coded path.

From NixOS
pkgs/development/python-modules/weasyprint/library-paths.patch

diff --git a/weasyprint/fonts.py b/weasyprint/fonts.py
index 377716c1..2016e01c 100644
--- a/weasyprint/fonts.py
+++ b/weasyprint/fonts.py
@@ -48,11 +48,8 @@ else:
     # with OSError: dlopen() failed to load a library: cairo / cairo-2
     # So let's hope we find the same file as cairo already did ;)
     # Same applies to pangocairo requiring pangoft2
-    fontconfig = dlopen(ffi, 'fontconfig', 'libfontconfig',
-                        'libfontconfig-1.dll',
-                        'libfontconfig.so.1', 'libfontconfig-1.dylib')
-    pangoft2 = dlopen(ffi, 'pangoft2-1.0', 'libpangoft2-1.0-0',
-                      'libpangoft2-1.0.so', 'libpangoft2-1.0.dylib')
+    fontconfig = dlopen(ffi, '@fontconfig@')
+    pangoft2 = dlopen(ffi, '@pangoft2@')
 
     ffi.cdef('''
         // FontConfig
diff --git a/weasyprint/text.py b/weasyprint/text.py
index 035074e9..08e40395 100644
--- a/weasyprint/text.py
+++ b/weasyprint/text.py
@@ -243,12 +243,9 @@ def dlopen(ffi, *names):
     return ffi.dlopen(names[0])  # pragma: no cover
 
 
-gobject = dlopen(ffi, 'gobject-2.0', 'libgobject-2.0-0', 'libgobject-2.0.so',
-                 'libgobject-2.0.dylib')
-pango = dlopen(ffi, 'pango-1.0', 'libpango-1.0-0', 'libpango-1.0.so',
-               'libpango-1.0.dylib')
-pangocairo = dlopen(ffi, 'pangocairo-1.0', 'libpangocairo-1.0-0',
-                    'libpangocairo-1.0.so', 'libpangocairo-1.0.dylib')
+gobject = dlopen(ffi, '@gobject@')
+pango = dlopen(ffi, '@pango@')
+pangocairo = dlopen(ffi, '@pangocairo@')
 
 gobject.g_type_init()
 
ion>
<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=bd200d351ac38979b37914467412d40ec849a248'>root</a>/<a href='/guix/log/.mailmap?id=bd200d351ac38979b37914467412d40ec849a248'>.mailmap</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/.mailmap?id=bd200d351ac38979b37914467412d40ec849a248&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-05-15 09:08:46 +0200'>2020-05-15</span></td><td><a href='/guix/commit/.mailmap?id=dff31d41d945bf4b25ad3014dac32561bfbb33a0'>mailmap: Update for self.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2020-05-13 09:30:26 +0300'>2020-05-13</span></td><td><a href='/guix/commit/.mailmap?id=3c986a7dc268756c097212de958f046b29b76c1b'>mailmap: Update entries for Nikita.</a><span class='msg-avail'>...</span></td><td>nikita</td></tr>
<tr><td><span title='2020-03-28 16:30:07 -0400'>2020-03-28</span></td><td><a href='/guix/commit/.mailmap?id=c2cf286c62933d2806ae17b8287520820bf87c7e'>Update email address and Savannah handle for Amin Bandali.</a><span class='msg-avail'>...</span></td><td>Amin Bandali</td></tr>
<tr><td><span title='2020-02-09 23:16:45 +0100'>2020-02-09</span></td><td><a href='/guix/commit/.mailmap?id=e81344428726f3dae5d2a2e7bb296f46fcde6cc5'>Update e-mail address for Jakob L. Kreuze.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-01-17 18:30:33 +0100'>2020-01-17</span></td><td><a href='/guix/commit/.mailmap?id=a3143063aeeecb5c02f75a6e1ddc0cc295e0e4f8'>Update email address for Amin Bandali.</a><span class='msg-avail'>...</span></td><td>Amin Bandali</td></tr>
<tr><td><span title='2019-12-19 11:35:23 -0600'>2019-12-19</span></td><td><a href='/guix/commit/.mailmap?id=4b3ff36228da17db980c98fe9e1669be613a5402'>Update email for Brett Gilio.</a><span class='msg-avail'>...</span></td><td>Brett Gilio</td></tr>
<tr><td><span title='2019-12-18 22:57:44 -0600'>2019-12-18</span></td><td><a href='/guix/commit/.mailmap?id=a7cdf124c0b28be6c4e750161c1341753eede7b8'>gnu: leocad: Update to 19.07.1.</a><span class='msg-avail'>...</span></td><td>Eric Bavier</td></tr>
<tr><td><span title='2019-05-03 08:45:55 +0200'>2019-05-03</span></td><td><a href='/guix/commit/.mailmap?id=3e85909044d8d9b492bcd2ecedde26d71794f145'>Correct email address for ison.</a><span class='msg-avail'>...</span></td><td>ison</td></tr>
<tr><td><span title='2019-03-18 15:05:08 +0100'>2019-03-18</span></td><td><a href='/guix/commit/.mailmap?id=47956fa0c24efcdcba3493f0231c30e9a39ec7df'>Correct name and email address for ng0.</a><span class='msg-avail'>...</span></td><td>ng0</td></tr>
<tr><td><span title='2019-01-21 10:10:43 +0100'>2019-01-21</span></td><td><a href='/guix/commit/.mailmap?id=e3634bd0a3480bde3aba5bd6d84d7aff25413207'>Update .mailmap.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2018-08-27 14:46:26 +0200'>2018-08-27</span></td><td><a href='/guix/commit/.mailmap?id=4715f92ef0b9650cc4075c69f17aa51e84da3f21'>Update email for Pierre Neidhardt.</a><span class='msg-avail'>...</span></td><td>Pierre Neidhardt</td></tr>
<tr><td><span title='2018-07-16 17:14:39 +0200'>2018-07-16</span></td><td><a href='/guix/commit/.mailmap?id=8bbb79cf95a07a40950448a8a09d888254404ed4'>mailmap: Add a line for Pierre-Antoine.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-07-16 16:53:50 +0200'>2018-07-16</span></td><td><a href='/guix/commit/.mailmap?id=33f4d14ab17096984404fc404b4539d784ecbf32'>mailmap: Add another line for myself.</a><span class='msg-avail'>...</span></td><td>Nils Gillmann</td></tr>
<tr><td><span title='2018-03-20 17:17:58 +0100'>2018-03-20</span></td><td><a href='/guix/commit/.mailmap?id=4a78fd4617908546be15d2c101f5cab512c71f8e'>Correct name and Email for ng0.</a><span class='msg-avail'>...</span></td><td>ng0</td></tr>
<tr><td><span title='2018-02-11 09:44:11 -0500'>2018-02-11</span></td><td><a href='/guix/commit/.mailmap?id=c275462025917ad7b8e182f29d6580804e585643'>mailmap: Adjust entries for ng0.</a><span class='msg-avail'>...</span></td><td>ng0</td></tr>
<tr><td><span title='2017-11-26 18:21:19 -0500'>2017-11-26</span></td><td><a href='/guix/commit/.mailmap?id=9221979e367a95c14a35236742792fb624d8e47c'>Update e-mail for ng0.</a><span class='msg-avail'>...</span></td><td>ng0</td></tr>
<tr><td><span title='2017-10-03 17:07:54 +0200'>2017-10-03</span></td><td><a href='/guix/commit/.mailmap?id=d109b1e85c5c1438e66dfc05ea4a018418edaf19'>Update e-mail for Theodoros Foradis.</a><span class='msg-avail'>...</span></td><td>Theodoros Foradis</td></tr>
<tr><td><span title='2017-08-29 20:13:24 -0400'>2017-08-29</span></td><td><a href='/guix/commit/.mailmap?id=3c8ba11a97d3f3b671b8919da8c41f0b0e2ccaf3'>Update e-mail for Kei Kebreau.</a><span class='msg-avail'>...</span></td><td>Kei Kebreau</td></tr>
<tr><td><span title='2017-08-13 16:11:48 -0400'>2017-08-13</span></td><td><a href='/guix/commit/.mailmap?id=79d5ad20e87066a0937a4b61a4857de2b34a7a30'>mailmap: fix entries for ng0.</a><span class='msg-avail'>...</span></td><td>ng0</td></tr>
<tr><td><span title='2017-06-16 15:48:17 +0300'>2017-06-16</span></td><td><a href='/guix/commit/.mailmap?id=a235ec3a6aa21980fe70e8d0c133e50986afbded'>mailmap: Adjust entries for ng0.</a><span class='msg-avail'>...</span></td><td>ng0</td></tr>