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

[Chuanqi Xu via cfe-commits]

================
@@ -41,9 +43,10 @@ Base::~Base() {}
 // CHECK: @_ZTSW3Mod4Base = constant
 // CHECK: @_ZTIW3Mod4Base = constant
 
-// CHECK-INLINE: @_ZTVW3Mod4Base = linkonce_odr {{.*}}unnamed_addr constant
-// CHECK-INLINE: @_ZTSW3Mod4Base = linkonce_odr {{.*}}constant
-// CHECK-INLINE: @_ZTIW3Mod4Base = linkonce_odr {{.*}}constant
+// With the new Itanium C++ ABI, the linkage of vtables in modules don't need to be linkonce ODR.
----------------
ChuanqiXu9 wrote:

While I agree `weak` may work here, I feel it is odd. I feel the default strong linkage seems better when it is applicable. What's the advance to use `weak` linkage here?

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