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

build/toolchain/gcc_toolchain.gni

Index: build/toolchain/gcc_toolchain.gni
diff --git a/build/toolchain/gcc_toolchain.gni b/build/toolchain/gcc_toolchain.gni
index be55c0fe8b34c408d8477f0f21f8aeac72bb74ec..faa09c4174ad7cdc764c11efd3c07aec81c65820 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -4,7 +4,6 @@
 
 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")
@@ -12,6 +11,13 @@ 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.