Avoid importing nacl config inside gcc_toolchain.gni for non-NaCl toolchains

build/toolchain/gcc_toolchain.gni

 # 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.
 
 import("//build/config/android/config.gni")
 import("//build/config/clang/clang.gni")
-import("//build/config/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/v8_target_cpu.gni")
 import("//build/toolchain/cc_wrapper.gni")
 import("//build/toolchain/clang_static_analyzer.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 
+if (is_nacl) {
+  # To keep NaCl variables out of builds that don't include NaCl, all
+  # variables defined in nacl/config.gni referenced here should be protected by
+  # is_nacl conditions.
+  import("//build/config/nacl/config.gni")
+}
+
 # Path to the Clang static analysis wrapper script.
 # REVIEWERS: can you suggest a better location for this?
 # GN is really picky about dead stores of variables except at the global scope.
 analyzer_wrapper =
     rebase_path("//build/toolchain/clang_static_analyzer_wrapper.py",
                 root_build_dir) + " --mode=clang"
 
 # This template defines a toolchain for something that works like gcc
 # (including clang).
 #
@@ skipping 541 matching lines @@
                            ])
 
     toolchain_args = {
       if (defined(invoker.toolchain_args)) {
         forward_variables_from(invoker.toolchain_args, "*")
       }
       is_clang = true
     }
   }
 }