Un-comment-out code using API change from clang

This will compile now that the automerger from llvm succeeded.

Author: akyrtzi

lib/ClangImporter/ClangImporter.cpp

@@ -821,8 +821,8 @@ bool ClangImporter::canReadPCH(StringRef PCHFilename) {
                              &Impl.Instance->getModuleCache());
   auto invocation =
       std::make_shared<clang::CompilerInvocation>(*Impl.Invocation);
-  // invocation->getPreprocessorOpts().DisablePCHOrModuleValidation =
-  //     clang::DisableValidationForModuleKind::None;
+  invocation->getPreprocessorOpts().DisablePCHOrModuleValidation =
+      clang::DisableValidationForModuleKind::None;
   invocation->getPreprocessorOpts().AllowPCHWithCompilerErrors = false;
   invocation->getHeaderSearchOpts().ModulesValidateSystemHeaders = true;
   invocation->getLangOpts()->NeededByPCHOrCompilationUsesPCH = true;