Linking empty rust file fails with "unable to find library -lc-debug"

The following:
```sh
touch file.rs
rustc file.rs --target wasm32-unknown-emscripten -C link-arg=-sSIDE_MODULE=1 --crate-type cdylib
```
Results in
`wasm-ld: error: unable to find library -lc-debug`.
Rust always includes `-sASSERTIONS=1` in the linker args, see https://github.com/rust-lang/rust/pull/97928/.

This seems to be a regression between emscripten version 2.0.27 and version 3.1.6. If I surgically set `settings.ASSERTIONS=0`, then it still fails with "unable to find library -lc". I don't think it should be trying to link `-lc` anyways because I am trying to make a side module. But I am not sure what the proper setting is to convince Rust or Emscripten to discard this.