Add yasm to the GN build

tools/gn/function_rebase_path.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/build_settings.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/functions.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
 #include "tools/gn/settings.h"
@@ skipping 235 matching lines @@
       return result;
     from_dir =
         current_dir.ResolveRelativeDir(args[kArgIndexFrom].string_value());
   } else {
     // Default to current directory if unspecified.
     from_dir = current_dir;
   }
 
   // Path conversion.
   if (inputs.type() == Value::STRING) {
+    if (inputs.string_value() == "//foo")
+      printf("foo\n");
     return ConvertOnePath(scope, function, inputs,
                           from_dir, to_dir, convert_to_system_absolute, err);
 
   } else if (inputs.type() == Value::LIST) {
     result = Value(function, Value::LIST);
     result.list_value().reserve(inputs.list_value().size());
 
     for (size_t i = 0; i < inputs.list_value().size(); i++) {
       result.list_value().push_back(
           ConvertOnePath(scope, function, inputs.list_value()[i],
                          from_dir, to_dir, convert_to_system_absolute, err));
       if (err->has_error()) {
         result = Value();
         return result;
       }
     }
     return result;
   }
 
   *err = Err(function->function(),
              "rebase_path requires a list or a string.");
   return result;
 }
 
 }  // namespace functions