Update NaCl GN toolchain definitions.

src/trusted/service_runtime/linux/toolchain/BUILD.gn

Index: src/trusted/service_runtime/linux/toolchain/BUILD.gn
diff --git a/src/trusted/service_runtime/linux/toolchain/BUILD.gn b/src/trusted/service_runtime/linux/toolchain/BUILD.gn
index bbe9e531f88deae152a780839ebf737f5a0f6901..220c396770623970ea7e977d013656dc8fdff3d3 100644
--- a/src/trusted/service_runtime/linux/toolchain/BUILD.gn
+++ b/src/trusted/service_runtime/linux/toolchain/BUILD.gn
@@ -12,10 +12,12 @@ import("//build/toolchain/gcc_toolchain.gni")
 
 template("nacl_bootstrap_toolchain") {
   clang_toolchain(target_name) {
-    toolchain_cpu = invoker.toolchain_cpu
-    toolchain_os = target_os
-    use_debug_fission = false
-    use_gold = false
+    toolchain_args = {
+      current_cpu = invoker.toolchain_cpu
+      current_os = target_os
+      use_debug_fission = false
+      use_gold = false
+    }
   }
 }