Forward WrapperFrontendAction::shouldEraseOutputFiles()

[benlangmuir]

Summary

Per the documentation, this class is supposed to forward every virtual
method, but we had missed on (shouldEraseOutputFiles). This fixes using
a wrapped frontend action over the PCH generator when using
-fallow-pch-with-compiler-errors. I do not think any upstream wrapper
actions can test this.

rdar://61110294

clang/include/clang/Frontend/FrontendAction.h

 protected:
   bool PrepareToExecuteAction(CompilerInstance &CI) override;
   std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                  StringRef InFile) override;
   bool BeginInvocation(CompilerInstance &CI) override;
   bool BeginSourceFileAction(CompilerInstance &CI) override;
   void ExecuteAction() override;
   void EndSourceFileAction() override;
+  bool shouldEraseOutputFiles() override;
 
 public:
   /// Construct a WrapperFrontendAction from an existing action, taking
   /// ownership of it.
   WrapperFrontendAction(std::unique_ptr<FrontendAction> WrappedAction);
 
   bool usesPreprocessorOnly() const override;
   TranslationUnitKind getTranslationUnitKind() override;

clang/lib/Frontend/FrontendAction.cpp

bool WrapperFrontendAction::BeginSourceFileAction(CompilerInstance &CI) {
   return Ret;
 }
 void WrapperFrontendAction::ExecuteAction() {
   WrappedAction->ExecuteAction();
 }
 void WrapperFrontendAction::EndSourceFileAction() {
   WrappedAction->EndSourceFileAction();
 }
+bool WrapperFrontendAction::shouldEraseOutputFiles() {
+  return WrappedAction->shouldEraseOutputFiles();
+}
 
 bool WrapperFrontendAction::usesPreprocessorOnly() const {
   return WrappedAction->usesPreprocessorOnly();
 }
 TranslationUnitKind WrapperFrontendAction::getTranslationUnitKind() {
   return WrappedAction->getTranslationUnitKind();
 }
 bool WrapperFrontendAction::hasPCHSupport() const {