[Mac/iOS/GN] Allow targets to override the output directory.

build/config/mac/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/toolchain/toolchain.gni")
 
 # This is used as the base template for both iOS and Mac frameworks..
 #
 # Arguments
 #
@@ skipping 39 matching lines @@
                            [
                              "assert_no_deps",
                              "data_deps",
                              "info_plist",
                              "output_name",
                              "visibility",
                            ])
     output_name = _output_name
     output_prefix_override = true
     output_extension = ""
+    output_dir = "$target_out_dir/$_shared_library_target"
   }
 
   bundle_data(_shared_library_bundle_data) {
     visibility = [ ":$_framework_target" ]
     forward_variables_from(invoker, [ "testonly" ])
     sources = [
-      "$root_out_dir/${_output_name}",
+      "$target_out_dir/$_shared_library_target/$_output_name",
     ]
     outputs = [
       "{{bundle_executable_dir}}/$_output_name",
     ]
     public_deps = [
       ":$_shared_library_target",
     ]
   }
 
   create_bundle(_framework_target) {
@@ skipping 87 matching lines @@
 
   framework_bundle(target_name) {
     forward_variables_from(invoker, "*", [ "info_plist" ])
 
     if (!defined(deps)) {
       deps = []
     }
     deps += [ ":$_info_plist_bundle_data" ]
   }
 }