Add a CC1 option -verify-pch

This option will:
- load the given pch file
- verify it is not out of date by stat'ing dependencies, and
- return 0 on success and non-zero on error

llvm-svn: 200884

clang/lib/Frontend/CompilerInvocation.cpp

@@ -700,6 +700,8 @@ static InputKind ParseFrontendArgs(FrontendOptions &Opts, ArgList &Args,
       Opts.ProgramAction = frontend::ParseSyntaxOnly; break;
     case OPT_module_file_info:
       Opts.ProgramAction = frontend::ModuleFileInfo; break;
+    case OPT_verify_pch:
+      Opts.ProgramAction = frontend::VerifyPCH; break;
     case OPT_print_decl_contexts:
       Opts.ProgramAction = frontend::PrintDeclContext; break;
     case OPT_print_preamble:
@@ -1585,6 +1587,7 @@ static void ParsePreprocessorOutputArgs(PreprocessorOutputOptions &Opts,
   case frontend::GeneratePTH:
   case frontend::ParseSyntaxOnly:
   case frontend::ModuleFileInfo:
+  case frontend::VerifyPCH:
   case frontend::PluginAction:
   case frontend::PrintDeclContext:
   case frontend::RewriteObjC: