Frontend: Inherit compiler debugging options during module interface actions.

When building a module interface for the -typecheck-module-from-interface or
-compile-module-from-interface actions, inherit and honor compiler debugging
options and emit debugging output at the end of the interface build.

lib/Frontend/ModuleInterfaceBuilder.cpp

@@ -203,6 +203,7 @@ std::error_code ExplicitModuleInterfaceBuilder::buildSwiftModuleFromInterface(
     ArrayRef<std::string> CompiledCandidates,
     StringRef CompilerVersion) {
   auto Invocation = Instance.getInvocation();
+
   // Try building forwarding module first. If succeed, return.
   if (Instance.getASTContext()
           .getModuleInterfaceChecker()
@@ -254,6 +255,9 @@ std::error_code ExplicitModuleInterfaceBuilder::buildSwiftModuleFromInterface(
                  builtByCompiler);
       }
     }
+
+    // If requested, dump debugging output before exiting.
+    Instance.emitEndOfPipelineDebuggingOutput();
   };
 
   Instance.performSema();