Dynamic Libraries: RuntimeError function signature mismatch

Hi!

Similar to my previous issues, here is another fairly simplified test case, which results in the following error during WASM instantiation:
```
Uncaught (in promise) RuntimeError: function signature mismatch
at _ZN8Standard8AllocateEm (:wasm-function[23]:0x1379)
at obj. (https://embind-dynamic-libs-03-git-master.donalffons.vercel.app/emscripten/build/main.js:2037:31)
at _ZN18Standard_TransientnwEm (:wasm-function[4]:0x200)
at :wasm-function[3]:0x1c8
at :wasm-function[5]:0x219
at __post_instantiate (:wasm-function[1]:0x1b6)
at callRuntimeCallbacks (https://embind-dynamic-libs-03-git-master.donalffons.vercel.app/emscripten/build/main.js:1747:11)
at initRuntime (https://embind-dynamic-libs-03-git-master.donalffons.vercel.app/emscripten/build/main.js:1361:3)
at doRun (https://embind-dynamic-libs-03-git-master.donalffons.vercel.app/emscripten/build/main.js:52650:5)
at run (https://embind-dynamic-libs-03-git-master.donalffons.vercel.app/emscripten/build/main.js:52672:5)
```
Repo: https://github.com/donalffons/embind-dynamicLibs-03
Live Example: https://embind-dynamic-libs-03-git-master.donalffons.vercel.app/javascript

- As before, the code is stripped down from a fairly large code base
- As before, there seems to be a race condition: Sometimes, WASM instantiation works as expected, sometimes it raises the error. For me, the web-hosted live examples runs without issues most of the time. On localhost, I see the error almost always.
- There is one MAIN_MODULE and 2 SIDE_MODULEs (named library1 and library2). Again, there is no Embind code.
- All what library2 does, is [`auto a = Standard::Allocate();`](https://github.com/donalffons/embind-dynamicLibs-03/blob/master/emscripten/library2.cxx#L3). This method is [implemented in library1](https://github.com/donalffons/embind-dynamicLibs-03/blob/master/emscripten/library1.cxx#L12):
```cpp
class Standard_MMgrRaw
{
public:
virtual void* Allocate() {
return new int;
}
};

void* Standard::Allocate()
{
std::cout << "1" << std::endl;
auto a = new Standard_MMgrRaw ();
std::cout << "2" << std::endl;
auto b = a->Allocate(); // RuntimeError: Function signature mismatch
std::cout << "3" << std::endl;
return b;
}
```

Full disclosure: This is most probably the same issue as #13026, but I was hoping to get your attention towards this test case with a new issue.

I would greatly appreciate help with this, as this is a major blocking point for my project.