Add forward_variables_from() and target() to GN

tools/gn/BUILD.gn

 # 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.
 
 import("//testing/test.gni")
 
 defines = [ "GN_BUILD" ]
 
 static_library("gn_lib") {
   configs += [ "//build/config:precompiled_headers" ]
@@ skipping 42 matching lines @@
     "err.cc",
     "err.h",
     "escape.cc",
     "escape.h",
     "exec_process.cc",
     "exec_process.h",
     "filesystem_utils.cc",
     "filesystem_utils.h",
     "function_exec_script.cc",
     "function_foreach.cc",
+    "function_forward_variables_from.cc",
     "function_get_label_info.cc",
     "function_get_path_info.cc",
     "function_get_target_outputs.cc",
     "function_process_file_template.cc",
     "function_read_file.cc",
     "function_rebase_path.cc",
     "function_set_default_toolchain.cc",
     "function_set_defaults.cc",
     "function_template.cc",
     "function_toolchain.cc",
@@ skipping 167 matching lines @@
     "action_target_generator_unittest.cc",
     "args_unittest.cc",
     "builder_unittest.cc",
     "c_include_iterator_unittest.cc",
     "command_format_unittest.cc",
     "config_values_extractors_unittest.cc",
     "escape_unittest.cc",
     "exec_process_unittest.cc",
     "filesystem_utils_unittest.cc",
     "function_foreach_unittest.cc",
+    "function_forward_variables_from_unittest.cc",
     "function_get_label_info_unittest.cc",
     "function_get_path_info_unittest.cc",
     "function_get_target_outputs_unittest.cc",
     "function_process_file_template_unittest.cc",
     "function_rebase_path_unittest.cc",
     "function_write_file_unittest.cc",
     "functions_target_unittest.cc",
     "functions_unittest.cc",
     "header_checker_unittest.cc",
     "inherited_libraries_unittest.cc",
@@ skipping 44 matching lines @@
 }
 
 executable("generate_test_gn_data") {
   sources = [
     "generate_test_gn_data.cc",
   ]
   deps = [
     "//base",
   ]
 }