Convert GN single-item list concat to use lists.

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.
 
 gyp_file = "gn.gyp"
 external = true
 
 # Not defined when doing a GYP build, this lets the code key off of GN-specific
 # features (the last change target). This can be removed when the last change
 # target is supported by the GN->GYP converter (see is_gyp conditional for that
@@ skipping 159 matching lines @@
 executable("gn") {
   sources = [
     "gn_main.cc",
   ]
 
   deps = [
     ":gn_lib",
   ]
   if (!is_gyp) {
     # Currently this only works in GYP (see GN_BUILD above).
-    deps += "//build/util:last_change"
+    deps += [ "//build/util:last_change" ]
   }
 }
 
 test("gn_unittests") {
   sources = [
     "builder_unittest.cc",
     "escape_unittest.cc",
     "file_template_unittest.cc",
     "filesystem_utils_unittest.cc",
     "function_rebase_path_unittest.cc",
@@ skipping 24 matching lines @@
     "//base/test:run_all_unittests",
     "//base/test:test_support_base",
     "//testing/gtest",
   ]
 }
 
 executable("generate_test_gn_data") {
   sources = [ "generate_test_gn_data.cc" ]
   deps = [ "//base" ]
 }