Make GN unit tests single process.

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.
 
 defines = [ "GN_BUILD" ]
 
 static_library("gn_lib") {
   sources = [
     "action_target_generator.cc",
     "action_target_generator.h",
@@ skipping 182 matching lines @@
     "ninja_action_target_writer_unittest.cc",
     "ninja_binary_target_writer_unittest.cc",
     "ninja_copy_target_writer_unittest.cc",
     "ninja_helper_unittest.cc",
     "ninja_target_writer_unittest.cc",
     "operators_unittest.cc",
     "parse_tree_unittest.cc",
     "parser_unittest.cc",
     "path_output_unittest.cc",
     "pattern_unittest.cc",
+    "run_all_unittests.cc",
     "scope_per_file_provider_unittest.cc",
     "scope_unittest.cc",
     "source_dir_unittest.cc",
     "string_utils_unittest.cc",
     "target_generator_unittest.cc",
     "target_unittest.cc",
     "template_unittest.cc",
     "test_with_scope.cc",
     "test_with_scope.h",
     "tokenizer_unittest.cc",
     "value_unittest.cc",
     "visibility_unittest.cc",
   ]
   deps = [
     ":gn_lib",
-    "//base/test:run_all_unittests",
     "//base/test:test_support",
     "//testing/gtest",
   ]
 }
 
 executable("generate_test_gn_data") {
   sources = [ "generate_test_gn_data.cc" ]
   deps = [ "//base" ]
 }