Convert GN single-item list concat to use lists.

build/config/BUILDCONFIG.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.
 
 # =============================================================================
 # BUILD FLAGS
 # =============================================================================
 #
 # This block lists input arguments to the build, along with their default
 # values. GN requires listing them explicitly so it can validate input and have
@@ skipping 310 matching lines @@
   "//build/config/compiler:chromium_code",
   "//build/config/compiler:default_warnings",
   "//build/config/compiler:no_rtti",
   "//build/config/compiler:runtime_library",
 ]
 if (is_win) {
   native_compiler_configs += [
     "//build/config/win:sdk",
   ]
 } else if (is_clang) {
-  native_compiler_configs += "//build/config/clang:find_bad_constructs"
+  native_compiler_configs += [ "//build/config/clang:find_bad_constructs" ]
 }
 
 # Optimizations and debug checking.
 if (is_debug) {
-  native_compiler_configs += "//build/config:debug"
+  native_compiler_configs += [ "//build/config:debug" ]
   default_optimization_config = "//build/config/compiler:no_optimize"
 } else {
-  native_compiler_configs += "//build/config:release"
+  native_compiler_configs += [ "//build/config:release" ]
   default_optimization_config = "//build/config/compiler:optimize"
 }
-native_compiler_configs += default_optimization_config
+native_compiler_configs += [ default_optimization_config ]
 
 # Symbol setup.
 if (is_clang && (is_linux || is_android)) {
   # Clang creates chubby debug information, which makes linking very slow.
   # For now, don't create debug information with clang.
   # See http://crbug.com/70000
   # TODO(brettw) This just copies GYP. Why not do this on Mac as well?
   default_symbols_config = "//build/config/compiler:no_symbols"
 } else if (symbol_level == 2) {
   default_symbols_config = "//build/config/compiler:symbols"
 } else if (symbol_level == 1) {
   default_symbols_config = "//build/config/compiler:minimal_symbols"
 } else if (symbol_level == 0) {
   default_symbols_config = "//build/config/compiler:no_symbols"
 } else {
   assert(false, "Bad value for symbol_level.")
 }
-native_compiler_configs += default_symbols_config
+native_compiler_configs += [ default_symbols_config ]
 
 # Windows linker setup for EXEs and DLLs.
 if (is_win) {
   if (is_debug) {
     default_incremental_linking_config =
       "//build/config/win:incremental_linking"
   } else {
     default_incremental_linking_config =
       "//build/config/win:no_incremental_linking"
   }
   windows_linker_configs = [
     default_incremental_linking_config,
     "//build/config/win:sdk_link",
     "//build/config/win:common_linker_setup",
     # Default to console-mode apps. Most of our targets are tests and such
     # that shouldn't use the windows subsystem.
     "//build/config/win:console",
   ]
 }
 
 set_defaults("executable") {
   configs = native_compiler_configs
   if (is_win) {
     configs += windows_linker_configs
   } else if (is_mac) {
-    configs += "//build/config/mac:mac_dynamic_flags"
+    configs += [ "//build/config/mac:mac_dynamic_flags" ]
   } else if (is_linux) {
-    configs += "//build/config/linux:executable_ldconfig"
+    configs += [ "//build/config/linux:executable_ldconfig" ]
   }
 }
 
 set_defaults("static_library") {
   configs = native_compiler_configs
 }
 
 set_defaults("shared_library") {
   configs = native_compiler_configs
   if (is_win) {
     configs += windows_linker_configs
   } else if (is_mac) {
-    configs += "//build/config/mac:mac_dynamic_flags"
+    configs += [ "//build/config/mac:mac_dynamic_flags" ]
   }
 }
 
 set_defaults("source_set") {
   configs = native_compiler_configs
 }
 
 # ==============================================================================
 # TOOLCHAIN SETUP
 # ==============================================================================
@@ skipping 20 matching lines @@
 } else if (is_android) {
   host_toolchain = "//build/toolchain/linux:$build_cpu_arch"
   set_default_toolchain("//build/toolchain/android:$cpu_arch")
 } else if (is_linux) {
   host_toolchain = "//build/toolchain/linux:$build_cpu_arch"
   set_default_toolchain("//build/toolchain/linux:$cpu_arch")
 } else if (is_mac || is_ios) {
   host_toolchain = "//build/toolchain/mac:clang"
   set_default_toolchain(host_toolchain)
 }