Trouble with emcc 6.0.0 from #25930

I'm not 100% sure what the problem is but emcc 6.0.0 works fine for me if I revert #25930. The problem is that `-Bstatic` is passed when I'm trying to link a static library.

I think the problem is that the condition here is wrong:
```py
if settings.FAKE_DYLIBS or (not settings.MAIN_MODULE and not settings.SIDE_MODULE):
cmd.append('-Bstatic')
else:
# wasm-ld still defaults to static linking by default. If that ever changes, we can remove this line.
cmd.append('-Bdynamic')
```
https://github.com/emscripten-core/emscripten/blob/6d8b2c1707b0a7c3dab396d064848ad6f4364346/tools/building.py#L167-L172