Fix the Linux shared build.

third_party/libxml/libxml.gyp

 # Copyright (c) 2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'conditions': [
       ['OS=="linux" or OS=="freebsd"', {'os_include': 'linux'}],
       ['OS=="mac"', {'os_include': 'mac'}],
       ['OS=="win"', {'os_include': 'win32'}],
@@ skipping 156 matching lines @@
           'direct_dependent_settings': {
             'defines': [
               'LIBXML_STATIC',
             ],
             'include_dirs': [
               '<(os_include)/include',
               'include',
             ],
           },
           'conditions': [
+            ['OS=="linux"', {
+              'link_settings': {
+                'libraries': [
+                  # We need dl for dlopen() and friends.
+                  '-ldl',
+                ],
+              },
+            }],
             ['OS=="mac"', {'defines': ['_REENTRANT']}],
             ['OS=="win"', {
               'product_name': 'libxml2',
             }, {  # else: OS!="win"
               'product_name': 'xml2',
             }],
           ],
         }],
       ],
     },
   ],
 }