I guess you mean the node_modules folder, where in fact this makes a lot of sense. What OP means is the build folder to which the frontend part of project is compiled.

I've been contemplating just checking in the build folder.

It does feel like a code smell, but it'd make deployment easier.

Our frontend is Javascript, wherein there's no worry about native modules.

Our backend is Python running Pypy, so there's no native code there either.