[NFC] [C++20] [Modules] [Reduced BMI] Reorder Emitting reduced BMI and normal BMI for named modules

When we generate the reduced BMI on the fly, the order of the emitting
phase is different within `-emit-obj` and `-emit-module-interface`.
Although this is meant to be fine, we observed it in
#93859 (that the different phase order may cause problems).
Also it turns out to be a different fundamental reason to the orders.

But it might be fine to make the order of emitting reducing BMI at first
to avoid such confusions in the future.

Author: ChuanqiXu9

clang/lib/Frontend/FrontendActions.cpp

@@ -273,9 +273,6 @@ std::unique_ptr<ASTConsumer>
 GenerateModuleInterfaceAction::CreateASTConsumer(CompilerInstance &CI,
                                                  StringRef InFile) {
   std::vector<std::unique_ptr<ASTConsumer>> Consumers;
-  Consumers.push_back(std::make_unique<CXX20ModulesGenerator>(
-      CI.getPreprocessor(), CI.getModuleCache(),
-      CI.getFrontendOpts().OutputFile));
 
   if (CI.getFrontendOpts().GenReducedBMI &&
       !CI.getFrontendOpts().ModuleOutputPath.empty()) {
@@ -284,6 +281,10 @@ GenerateModuleInterfaceAction::CreateASTConsumer(CompilerInstance &CI,
         CI.getFrontendOpts().ModuleOutputPath));
   }
 
+  Consumers.push_back(std::make_unique<CXX20ModulesGenerator>(
+      CI.getPreprocessor(), CI.getModuleCache(),
+      CI.getFrontendOpts().OutputFile));
+
   return std::make_unique<MultiplexConsumer>(std::move(Consumers));
 }