GN: Simplify config by unconditionalising a flag that nacl-clang recognises

Use of the flag "-Wno-inconsistent-missing-override" no longer needs
to be conditionalised.

This is also a step towards getting Skia to build with the (P)NaCl
toolchains, because Skia currently needs to be compiled with this
warning disabled.

BUG=https://github.com/domokit/mojo/issues/431
TEST=build
R=smklein@chromium.org

Review URL: https://codereview.chromium.org/1349933003 .
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index ce7b7c5..d595dc8 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -935,18 +935,10 @@
 
     # TODO(thakis): Remove, http://crbug.com/263960
     "-Wno-reserved-user-defined-literal",
-  ]
 
-  # NaCl's Clang compiler and Chrome's hermetic Clang compiler will almost
-  # always have different versions. Certain flags may not be recognized by
-  # one version or the other.
-  if (!is_nacl) {
-    # Flags NaCl does not recognize.
-    default_warning_flags += [
-      # TODO(hans): Get this cleaned up.
-      "-Wno-inconsistent-missing-override",
-    ]
-  }
+    # TODO(hans): Get this cleaned up.
+    "-Wno-inconsistent-missing-override",
+  ]
 }
 
 # chromium_code ---------------------------------------------------------------