pthread_create detected as undefined symbol with side module + -fexception + -O3

Hello,

When creating a side module with the pthread option, an assertion occured during the loading of the side module when compilation includes the `-fexceptions` and `-O3`. In my project, the `-fexceptions` is mandatory so I did the small example to check this problem.

Compilation:
```
REM Step 1: Remove previous compilation
CALL rm *.html *.wasm *.js *.o *.tmp*

REM Step 2: Compilation Options
CALL em++ -c Side.cpp -pthread -fPIC -fexceptions -O3 -o foo2.o
CALL em++ -c Main.cpp -pthread -fPIC -fexceptions -O3 -o Main.o

REM Step 3: Create WASM libraries using SIDE_MODULE
CALL em++ foo2.o -s SIDE_MODULE=1 -s EXPORT_ALL=1 -pthread -fPIC -o foo2.wasm

REM Step 4: Execute without Side_Module
CALL em++ -pthread -s MAIN_MODULE=1 -s PROXY_TO_PTHREAD -s ALLOW_MEMORY_GROWTH=1 -fPIC -s EXIT_RUNTIME=1 Main.o -s RUNTIME_LINKED_LIBS="['foo2.wasm']" -o Test.html
```

The callstack is the following:
```
Test.html:1246 Assertion failed: Missing signature argument to addFunction: function _pthread_create(pthread_ptr, attr, start_routine, arg) {
if (typeof SharedArrayBuffer === "undefined") {
err("Current environment does not support SharedArrayBuffer, pthreads are not available!");
return 6;
...
printErr @ Test.html:1246
abort @ Test.js:1273
assert @ Test.js:655
addFunctionWasm @ Test.js:512
reportUndefinedSymbols @ Test.js:2425
(anonymous) @ Test.js:2455
Promise.then (async)
preloadDylibs @ Test.js:2453
run @ Test.js:48460
runCaller @ Test.js:48421
removeRunDependency @ Test.js:1256
receiveInstance @ Test.js:1379
receiveInstantiationResult @ Test.js:1389
Promise.then (async)
(anonymous) @ Test.js:1409
Promise.then (async)
instantiateAsync @ Test.js:1407
createWasm @ Test.js:1428
(anonymous) @ Test.js:32966
```

I investigated the `pthread_create` appearances in the binary file (`Test.wasm`) and saw these two lines:
```
(func $env.pthread_create (;16;) (import "env" "pthread_create") (param i32 i32 i32 i32) (result i32))

(global $GOT.func.pthread_create (;14;) (import "GOT.func" "pthread_create") (mut i32))
```
The second one will fill the GOT table which is why `pthread_create` appears as an undefined symbol.

Result:

If I remove the `-O3` option, it will return the `heap memory area (address zero)!` issue.
This is the current of my analysis, any suggestions to help me solve this problem are welcomed.

My snippet code:
**Main.cpp**
```
int side_main();
int main()
{

side_main();
return 0;
}
```
**Side.cpp**
```
// thread example
#include // std::cout
#include // std::thread
#include
#include
#include //sleep
#define NUM_THREADS 5

void foo()
{
std::cout <<"Check foo()"<< std::endl;
}

void bar(int x)
{
std::cout <<"Check bar(x)"<< std::endl;
}

int side_main()
{
std::thread first (foo); // spawn new thread that calls foo()
std::thread second (bar,0); // spawn new thread that calls bar(0)
std::cout << "main, foo and bar now execute concurrently...\n";
// synchronize threads:
first.join(); // pauses until first finishes
second.join(); // pauses until second finishes
std::cout << "foo and bar completed.\n";
return 0;
}

```