gn: Support build directories outside the source tree.

tools/gn/function_get_target_outputs.cc

 // Copyright 2014 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/build_settings.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/settings.h"
 #include "tools/gn/substitution_writer.h"
 #include "tools/gn/target.h"
@@ skipping 61 matching lines @@
                           const FunctionCallNode* function,
                           const std::vector<Value>& args,
                           Err* err) {
   if (args.size() != 1) {
     *err = Err(function, "Expected one argument.");
     return Value();
   }
 
   // Resolve the requested label.
   Label label = Label::Resolve(scope->GetSourceDir(),
-                               ToolchainLabelForScope(scope), args[0], err);
+                               ToolchainLabelForScope(scope), args[0],
+                               scope->settings()->build_settings()->root_path(),
+                               err);
   if (label.is_null())
     return Value();
 
   // Find the referenced target. The targets previously encountered in this
   // scope will have been stashed in the item collector (they'll be dispatched
   // when this file is done running) so we can look through them.
   const Target* target = NULL;
   Scope::ItemVector* collector = scope->GetItemCollector();
   if (!collector) {
     *err = Err(function, "No targets defined in this context.");
@@ skipping 39 matching lines @@
   // Convert to Values.
   Value ret(function, Value::LIST);
   ret.list_value().reserve(files.size());
   for (const auto& file : files)
     ret.list_value().push_back(Value(function, file.value()));
 
   return ret;
 }
 
 }  // namespace functions