GN: toolchain threading cleanup

tools/gn/ninja_copy_target_writer.cc

Index: tools/gn/ninja_copy_target_writer.cc
diff --git a/tools/gn/ninja_copy_target_writer.cc b/tools/gn/ninja_copy_target_writer.cc
index 5de249fa457a734bb9278c0070d1281870719935..89b3e3fb52dfa7656594bcf8b1ac015c8906b6db 100644
--- a/tools/gn/ninja_copy_target_writer.cc
+++ b/tools/gn/ninja_copy_target_writer.cc
@@ -9,8 +9,9 @@
 #include "tools/gn/string_utils.h"
 
 NinjaCopyTargetWriter::NinjaCopyTargetWriter(const Target* target,
+                                             const Toolchain* toolchain,
                                              std::ostream& out)
-    : NinjaTargetWriter(target, out) {
+    : NinjaTargetWriter(target, toolchain, out) {
 }
 
 NinjaCopyTargetWriter::~NinjaCopyTargetWriter() {
@@ -22,8 +23,7 @@ void NinjaCopyTargetWriter::Run() {
 
   std::vector<OutputFile> output_files;
 
-  std::string rule_prefix =
-      helper_.GetRulePrefix(target_->settings()->toolchain());
+  std::string rule_prefix = helper_.GetRulePrefix(target_->settings());
 
   for (size_t i = 0; i < target_->sources().size(); i++) {
     const SourceFile& input_file = target_->sources()[i];