Fix non-portable path warning in DiagnosticLexKinds.td

Author: gmh5225

clang/include/clang/Basic/DiagnosticLexKinds.td

@@ -347,7 +347,7 @@ class NonportablePath  : Warning<
   "non-portable path to file '%0'; specified path differs in case from file"
   " name on disk">;
 def pp_nonportable_path : NonportablePath,
-  InGroup<DiagGroup<"nonportable-include-path">>;
+  InGroup<DiagGroup<"nonportable-include-path">>, DefaultIgnore;
 def pp_nonportable_system_path : NonportablePath, DefaultIgnore,
   InGroup<DiagGroup<"nonportable-system-include-path">>;