I found a solution to my problem. In the RequireJS config I've added:
requirejs.config({
paths: {
nls: "/js/nls"
}
});
Because the path starts with a slash, RequireJS knows it's not relative. Now the problem I got was that the build would fail, as RequireJS would be looking for default language files in /js/nls. Therefore, I added a symlink from the root of my webserver to the nls directory on the machine.