Allow GN toolchains to specify runtime deps outputs.

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 271 matching lines @@
     "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_toolchain_unittest.cc",
     "function_write_file_unittest.cc",
     "functions_target_unittest.cc",
     "functions_unittest.cc",
     "header_checker_unittest.cc",
     "inherited_libraries_unittest.cc",
     "input_conversion_unittest.cc",
     "label_pattern_unittest.cc",
     "label_unittest.cc",
     "loader_unittest.cc",
     "ninja_action_target_writer_unittest.cc",
@@ skipping 35 matching lines @@
     "format_test_data/",
   ]
 
   deps = [
     ":gn_lib",
     "//base/test:run_all_unittests",
     "//base/test:test_support",
     "//testing/gtest",
   ]
 }