ReferenceError: _setThrew is not defined when linking as C++

**Version of emscripten/emsdk:**
emscripten/emsdk:3.1.56 (a little behind I know, but I couldn't see any recent changes that looked relevant. I will try updating soon.)

I think this is a follow up to #21381. I have no compilation errors, but despite the `invoke_` functions depending on `_setThrew`, it isn't defined.

```
function invoke_vi(index, a1) {
var sp = stackSave();
try {
dynCall_vi(index, a1);
} catch (e) {
stackRestore(sp);
if (e !== e + 0) throw e;
_setThrew(1, 0);
}
}
```

I suspect this may be happening because I've set `set_target_properties(${target} PROPERTIES LINKER_LANGUAGE CXX)` in CMake, but there are no actual C++ files being linked in? (We previously determined that my project needs to be linked as CXX because it's using Rust.)