Add gn_unittests to linux bots.

tools/gn/run_all_unittests.cc

Index: tools/gn/run_all_unittests.cc
diff --git a/tools/gn/run_all_unittests.cc b/tools/gn/run_all_unittests.cc
deleted file mode 100644
index 77b9e54788cd23c7b8e3ed050a809dc0a9eda0df..0000000000000000000000000000000000000000
--- a/tools/gn/run_all_unittests.cc
+++ /dev/null
@@ -1,12 +0,0 @@
-// Copyright 2014 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 "base/test/test_suite.h"
-
-// Don't use the multiprocess test harness. This test suite is fast enough and
-// it makes the output more difficult to read.
-int main(int argc, char** argv) {
-  base::TestSuite test_suite(argc, argv);
-  return test_suite.Run();
-}