Remove GN back-compat toolchain args code.

tools/gn/functions.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/functions.h"
 
 #include <stddef.h>
 #include <iostream>
 #include <utility>
 
@@ skipping 996 matching lines @@
     INSERT_FUNCTION(ProcessFileTemplate, false)
     INSERT_FUNCTION(ReadFile, false)
     INSERT_FUNCTION(RebasePath, false)
     INSERT_FUNCTION(SetDefaults, false)
     INSERT_FUNCTION(SetDefaultToolchain, false)
     INSERT_FUNCTION(SetSourcesAssignmentFilter, false)
     INSERT_FUNCTION(SplitList, false)
     INSERT_FUNCTION(Template, false)
     INSERT_FUNCTION(Tool, false)
     INSERT_FUNCTION(Toolchain, false)
-    INSERT_FUNCTION(ToolchainArgs, false)
     INSERT_FUNCTION(WriteFile, false)
 
     #undef INSERT_FUNCTION
   }
 };
 const FunctionInfoInitializer function_info;
 
 const FunctionInfoMap& GetFunctions() {
   return function_info.map;
 }
@@ skipping 72 matching lines @@
   }
 
   // Otherwise it's a no-block function.
   if (!VerifyNoBlockForFunctionCall(function, block, err))
     return Value();
   return found_function->second.no_block_runner(scope, function,
                                                 args.list_value(), err);
 }
 
 }  // namespace functions