Cleanup references to concurrent_links in gn binary.

tools/gn/toolchain.h

Index: tools/gn/toolchain.h
diff --git a/tools/gn/toolchain.h b/tools/gn/toolchain.h
index 4ccfdc8c699bcde4e4fa58f5f2bc4bc10671b95f..7b61f349b9c6065b9e9f0ecd7fb9316e0a127e37 100644
--- a/tools/gn/toolchain.h
+++ b/tools/gn/toolchain.h
@@ -124,16 +124,9 @@ class Toolchain : public Item {
     return substitution_bits_;
   }
 
-  void set_concurrent_links(int cl) { concurrent_links_ = cl; }
-  int concurrent_links() const { return concurrent_links_; }
-
  private:
   std::unique_ptr<Tool> tools_[TYPE_NUMTYPES];
 
-  // How many links to run in parallel. Only the default toolchain's version of
-  // this variable applies.
-  int concurrent_links_;
-
   bool setup_complete_;
 
   // Substitutions used by the tools in this toolchain.