ERROR_ON_UNDEFINED_SYMBOLS not useful in standalone mode

I compiled the following program that explicitly uses a WASI import to get randomness:

```c
#include
#include
#include

__attribute__((import_module("wasi_snapshot_preview1"),
import_name("random_get")))
int random_get(uint8_t* buffer, uint32_t length);

int getentropy(void* buffer, size_t length) {
return random_get(buffer, length);
}

int main() {
int fd = open("/dev/urandom", O_RDONLY);
assert(fd != -1);

uint8_t buffer[1024] = {};
int nread = read(fd, buffer, 1024);
assert(nread == 1024);

return *(unsigned int*)buffer % 126;
}
```

Compiling with `./emcc test.c -o test.wasm -sWASMFS -sSTANDALONE_WASM` gives the following error:

```