Finalize Swift debug info before running Clang codegen, because it may delete

the llvm module.

rdar://128309024

lib/IRGen/IRGenModule.cpp

@@ -1963,12 +1963,14 @@ bool IRGenModule::finalize() {
   }
   emitLazyPrivateDefinitions();
 
-  // Finalize clang IR-generation.
-  finalizeClangCodeGen();
-
+  // Finalize Swift debug info before running Clang codegen, because it may
+  // delete the llvm module.
   if (DebugInfo)
     DebugInfo->finalize();
 
+  // Finalize clang IR-generation.
+  finalizeClangCodeGen();
+
   // If that failed, report failure up and skip the final clean-up.
   if (!ClangCodeGen->GetModule())
     return false;