Update from chromium https://crrev.com/302282

third_party/libxml/libxml.gyp

 # Copyright (c) 2012 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': [
       # Define an "os_include" variable that points at the OS-specific generated
       # headers.  These were generated by running the configure script offline.
       ['os_posix == 1 and OS != "mac" and OS != "ios"', {
@@ skipping 33 matching lines @@
               'link_settings': {
                 'ldflags': [
                   '<!@(pkg-config --libs-only-L --libs-only-other libxml-2.0)',
                 ],
                 'libraries': [
                   '<!@(pkg-config --libs-only-l libxml-2.0)',
                 ],
               },
             }],
             ['OS == "ios"', {
-              'type': 'none',
+              'type': 'static_library',
+              'sources': [
+                'chromium/libxml_utils.h',
+                'chromium/libxml_utils.cc',
+              ],
+              'include_dirs': [
+                '$(SDKROOT)/usr/include/libxml2',
+              ],
               'all_dependent_settings': {
                 'defines': [
                   'USE_SYSTEM_LIBXML',
                 ],
                 'include_dirs': [
                   '$(SDKROOT)/usr/include/libxml2',
                 ],
               },
               'link_settings': {
                 'libraries': [
@@ skipping 178 matching lines @@
               # Disable unimportant 'unused variable' warning, and
               # signed/unsigned comparison warning. The signed/unsigned (4101)
               # is fixed upstream and can be removed eventually.
               # TODO(jschuh): http://crbug.com/167187 size_t -> int
               'msvs_disabled_warnings': [ 4018, 4101, 4267 ],
             }, {  # else: OS!="win"
               'product_name': 'xml2',
             }],
           ],
         }],
+        ['OS == "ios"', {
+          'toolsets': ['host', 'target'],
+        }],
       ],
     },
   ],
 }