fix(libc): ignore the guest DSO of thread atexit on Windows in the shared bridge

MinGW's __cxa_thread_atexit asserts dso is null or its own __dso_handle, so every guest export that forwards a guest module pointer needs the null rule, not only LibcInternalExtCxaThreadAtexit. The test now passes a non-host DSO on Windows too.

Co-Authored-By: Claude <noreply@anthropic.com>

core/libs/prx/libc/src/CxxAbiSupport.cpp

@@ -62,6 +62,9 @@ void* APS5_VABI __cxa_demangle_nid_postfix(const char* mangled, char* buf, std::
 }
 
 int APS5_VABI __cxa_thread_atexit_impl_nid_postfix(void (APS5_VABI *func)(void*), void* arg, void* dso) {
+#ifdef _WIN32
+    dso = nullptr;
+#endif
     struct ThreadAtexitContext {
         void (APS5_VABI *destructor)(void*);
         void* object;
@@ -88,12 +91,7 @@ int APS5_VABI __cxa_thread_atexit_nid_postfix(void (APS5_VABI *func)(void*), voi
 }
 
 int APS5_VABI LibcInternalExtCxaThreadAtexit_nid_postfix(void (APS5_VABI *destructor)(void*), void* object, void* module_id) {
-#ifdef _WIN32
-    (void)module_id;
-    return __cxa_thread_atexit_impl_nid_postfix(destructor, object, nullptr);
-#else
     return __cxa_thread_atexit_impl_nid_postfix(destructor, object, module_id);
-#endif
 }
 
 const std::error_category* _ZSt17iostream_categoryv_nid_postfix() { return &std::iostream_category(); }

core/libs/tests/GuestThreadCallbackAbi.cpp

@@ -57,9 +57,6 @@ int main() {
     }
 
     void* directDso = module;
-#ifdef _WIN32
-    directDso = nullptr;
-#endif
 
     int firstObject = 1;
     int secondObject = 2;