[iOS] Define build/config/ios:ios_dynamic_flags for default linker flags.

build/config/ios/rules.gni

 # Copyright 2015 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.
 
 import("//build/config/ios/ios_sdk.gni")
 import("//build/config/mac/base_rules.gni")
 import("//build/config/mac/symbols.gni")
 
 # Generates Info.plist files for Mac apps and frameworks.
 #
@@ skipping 158 matching lines @@
 
       if (defined(visibility)) {
         visibility += [ ":*($default_toolchain)" ]
       }
 
       output_name = _output_name
       if (!defined(libs)) {
         libs = []
       }
       libs += [ "UIKit.framework" ]
-      if (!defined(ldflags)) {
-        ldflags = []
-      }
-      ldflags += [ "-ObjC" ]
     }
   } else {
     # This is either a thin build or the default toolchain of a fat-build.
     # The template will expand in many different target ($target_name is the
     # create_bundle target) used as input to the create_bundle target.
     _generate_info_plist = target_name + "_generate_info_plist"
     _bundle_data_info_plist = target_name + "_bundle_data_info_plist"
 
     ios_info_plist(_generate_info_plist) {
       visibility = [ ":$_bundle_data_info_plist" ]
@@ skipping 63 matching lines @@
       if (_is_fat_build) {
         output_name = rebase_path(_arch_executable_path, root_build_dir)
       } else {
         output_name = rebase_path(_executable_path, root_build_dir)
       }
 
       if (!defined(libs)) {
         libs = []
       }
       libs += [ "UIKit.framework" ]
-      if (!defined(ldflags)) {
-        ldflags = []
-      }
-      ldflags += [ "-ObjC" ]
     }
 
     if (_is_fat_build) {
       # Create the multi-architecture binary from all the single architecture
       # binaries using "lipo". This target exists for the default toolchain
       # of a fat-build only and depends on the expansion of "ios_app_bundle"
       # for the other toolchains (i.e. a single "executable" target).
       #
       # This action only happens once per "ios_app_bundle" template (for the
       # main toolchain).
@@ skipping 568 matching lines @@
       public_deps = [
         ":$_framework_target+link$_toolchain_suffix",
       ]
     }
   }
 }
 
 set_defaults("ios_framework_bundle") {
   configs = default_shared_library_configs
 }