gn: Support build directories outside the source tree.

tools/gn/target_generator.cc

 // Copyright (c) 2013 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.
 
 #include "tools/gn/target_generator.h"
 
 #include "tools/gn/action_target_generator.h"
 #include "tools/gn/binary_target_generator.h"
 #include "tools/gn/build_settings.h"
 #include "tools/gn/config.h"
@@ skipping 300 matching lines @@
     }
   }
 
   return true;
 }
 
 bool TargetGenerator::FillGenericConfigs(const char* var_name,
                                          UniqueVector<LabelConfigPair>* dest) {
   const Value* value = scope_->GetValue(var_name, true);
   if (value) {
-    ExtractListOfUniqueLabels(*value, scope_->GetSourceDir(),
+    ExtractListOfUniqueLabels(scope_->settings()->build_settings(),
+                              *value, scope_->GetSourceDir(),
                               ToolchainLabelForScope(scope_), dest, err_);
   }
   return !err_->has_error();
 }
 
 bool TargetGenerator::FillGenericDeps(const char* var_name,
                                       LabelTargetVector* dest) {
   const Value* value = scope_->GetValue(var_name, true);
   if (value) {
-    ExtractListOfLabels(*value, scope_->GetSourceDir(),
+    ExtractListOfLabels(scope_->settings()->build_settings(),
+                        *value, scope_->GetSourceDir(),
                         ToolchainLabelForScope(scope_), dest, err_);
   }
   return !err_->has_error();
 }
 
 bool TargetGenerator::FillForwardDependentConfigs() {
   const Value* value = scope_->GetValue(
       variables::kForwardDependentConfigsFrom, true);
   if (value) {
-    ExtractListOfUniqueLabels(*value, scope_->GetSourceDir(),
+    ExtractListOfUniqueLabels(scope_->settings()->build_settings(),
+                              *value, scope_->GetSourceDir(),
                               ToolchainLabelForScope(scope_),
                               &target_->forward_dependent_configs(), err_);
   }
   return !err_->has_error();
 }