Remove old references to cpu_arch, os from GN files.

components/nacl/BUILD.gn

Index: components/nacl/BUILD.gn
diff --git a/components/nacl/BUILD.gn b/components/nacl/BUILD.gn
index 5074e3cb88992e3059c09f77d547238fe96c310d..b67835ccc154061291fc0c18c68a1b5f171e5c7d 100644
--- a/components/nacl/BUILD.gn
+++ b/components/nacl/BUILD.gn
@@ -37,13 +37,13 @@ if (enable_nacl) {
 
     if (enable_nacl_untrusted) {
       data_deps = [
-        # TODO(GYP): handle other cpu_arch's correctly.
+        # TODO(GYP): handle other architectures correctly.
         "//ppapi/native_client:nacl_irt(//native_client/build/toolchain/nacl:irt_x64)",
       ]
     }
     if (enable_pnacl) {
       data_deps += [
-        # TODO(GYP): handle other cpu_arch's correctly.
+        # TODO(GYP): handle other architectures correctly.
         "//ppapi/native_client/src/untrusted/pnacl_support_extension",
       ]
     }