[Cronet] Use xcode clang on iOS to reduce release binary size.

components/cronet/tools/package_ios.py

 #!/usr/bin/python
 # Copyright 2016 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.
 
 """
 package_ios.py - Build and Package Release and Rebug fat libraries for iOS.
 """
 
 import argparse
@@ skipping 72 matching lines @@
                                framework_name, 'Headers'),
                   os.path.join(out_dir, 'Headers'))
 
 
 def package_ios_framework_using_gn(out_dir='out/Framework', extra_options=''):
   print 'Building Cronet Dynamic Framework using gn...'
 
   # Package all builds in the output directory
   os.makedirs(out_dir)
   build_dir = ''
-  for (build_config, gn_extra_args) in [('Debug', 'is_debug=true'),
-        ('Release', 'is_debug=false enable_stripping=true')]:
+  for (build_config, gn_extra_args) in [('Debug', 'is_debug=true use_xcode_clang=true'),
+        ('Release', 'is_debug=false enable_stripping=true is_official_build=true')]:
     for (target_device, target_cpu, additional_cpu) in [('os', 'arm', 'arm64'),
         ('simulator', 'x86', 'x64')]:
       target_dir = '%s-iphone%s' % (build_config, target_device)
       build_dir = os.path.join("out", target_dir)
       gn_args = 'target_os="ios" enable_websockets=false ' \
                 'is_cronet_build=true is_component_build=false ' \
                 'disable_file_support=true disable_ftp_support=true ' \
                 'use_platform_icu_alternatives=true ' \
                 'disable_brotli_filter=true enable_dsyms=true ' \
                 'target_cpu="%s" additional_target_cpus = ["%s"] %s' % \
@@ skipping 85 matching lines @@
 
   if options.gn:
     return package_ios_framework_using_gn(out_dir, extra_options_list)
 
   return package_ios(out_dir, "out/Release", "opt") or \
          package_ios(out_dir, "out/Debug", "dbg")
 
 
 if __name__ == '__main__':
   sys.exit(main())