[clang] [C++20] [Modules] [Itanium ABI] Generate the vtable in the module unit of dynamic classes (PR #75912)

[Chuanqi Xu via cfe-commits]

================
@@ -318,6 +318,9 @@ namespace {
       if (Diags.hasUnrecoverableErrorOccurred())
         return;
 
+      if (RD->shouldEmitInExternalSource())
----------------
ChuanqiXu9 wrote:

I use `isInCurrentModuleUnit` instead since I feel the semantics are more clear.

https://github.com/llvm/llvm-project/pull/75912