Fix the output of "gn args" for the OS and CPU architecture.

tools/gn/secondary/build/config/BUILDCONFIG.gn

Index: tools/gn/secondary/build/config/BUILDCONFIG.gn
diff --git a/tools/gn/secondary/build/config/BUILDCONFIG.gn b/tools/gn/secondary/build/config/BUILDCONFIG.gn
index 1ae5e55d9b0e08617ba14d0b82124fdf05dd0703..78a3f27d82086468f9cfbeeaf4bab7dd1e3f27d2 100644
--- a/tools/gn/secondary/build/config/BUILDCONFIG.gn
+++ b/tools/gn/secondary/build/config/BUILDCONFIG.gn
@@ -34,10 +34,13 @@ declare_args() {
   is_clang = false
 
   # ASH is enabled.
+  # TODO(brettw) this should be moved out of the main build config file.
   use_ash = false
   # Aura is enabled.
+  # TODO(brettw) this should be moved out of the main build config file.
   use_aura = false
   # Ozone is enabled.
+  # TODO(brettw) this should be moved out of the main build config file.
   use_ozone = false
 }