Faulty assertion in node on .mjs files

It turns out that node will disable the global require function on foo.mjs - that is just not defined there, unlike for foo.js. I guess mjs files are modules and require is not supposed to be used there. This ends up a problem for us since we have an assertion on it:

https://github.com/emscripten-core/emscripten/blob/a3d8979b38d2f655f59b040bfd32f562ebc92d03/src/shell.js#L196-L198

Removing that assertion is necessary to run an .mjs file in node with -sASSERTIONS.

We should probably just remove it?

This happens on binaryen CI which will manually builds an .mjs file by concatenating the emcc output with some extra code.