Using WasmFS / OPFS from the main thread deadlocks on Safari

Please include the following in your bug report:

**Version of emscripten/emsdk:**
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.42 (6ede0b8fc1c979bb206148804bfb48b472ccc3da)
clang version 17.0.0 (https://github.com/llvm/llvm-project f3b64887de61020c09404bfee97b2fadd30df10a)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: ``

**Full link command and output with `-v` appended:**
emcc main.cpp -o hello.html -sWASMFS -pthread -sPTHREAD_POOL_SIZE=4

```cpp
#include
#include
#include

#include
#include

#include

extern "C"
{
std::thread* bgThread = nullptr;

EMSCRIPTEN_KEEPALIVE int main()
{
// Initialize wasmfs in bg thread
bgThread = new std::thread([]()
{
auto wasmfs_backend = wasmfs_create_opfs_backend();
const char* rootMount = "/persistent";
bool exists = access(rootMount, F_OK) == 0;
if (!exists)
wasmfs_create_directory(rootMount, 0777, wasmfs_backend);
});

// Keep the standard library runtime alive even after exiting main`
emscripten_exit_with_live_runtime();
return 0;
}

EMSCRIPTEN_KEEPALIVE void checkForDirectory()
{
bool exists = std::filesystem::exists("/persistent/data");
printf("exists = %d\n", exists);
}
}
```

Load the html with the necessary COOP settings (in order to get pthread to work). Then in the web debugger console, make a call to `window.Module._checkForDirectory()`. In Chrome, the output is printed out successfully. In Safari, the output is never printed out. The main thread is stuck in a tight loop, and the debugger is no longer useable. If there were other web workers running, their execution also seems to pause.