Convert GN single-item list concat to use lists.

tools/gn/secondary/ipc/BUILD.gn

 # Copyright (c) 2012 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.
 
 component("ipc") {
   external = true
   sources = [
     "file_descriptor_set_posix.cc",
     "file_descriptor_set_posix.h",
     "ipc_channel.cc",
@@ skipping 81 matching lines @@
     "ipc_sync_channel_unittest.cc",
     "ipc_sync_message_unittest.cc",
     "ipc_sync_message_unittest.h",
     "ipc_test_base.cc",
     "ipc_test_base.h",
     "sync_socket_unittest.cc",
     "unix_domain_socket_util_unittest.cc",
   ]
 
   if (is_win || is_ios) {
-    sources -= "unix_domain_socket_util_unittest.cc"
+    sources -= [ "unix_domain_socket_util_unittest.cc" ]
   }
   #if (is_android && gtest_target_type == "shared_library") {
   #  deps += "/testing/android/native_test.gyp:native_testNative_code"
   #}
   #if (is_posix && !is_mac && !is_android) {
   #  if (linux_use_tcmalloc) {
   #    deps += "/base/allocator"
   #  }
   #}
 
@@ skipping 44 matching lines @@
     "ipc_test_sink.cc",
     "ipc_test_sink.h",
   ]
   deps = [
     ":ipc",
     "//base",
     "//testing/gtest",
   ]
 }