Summary

Currently we use a local plugin plugin-wrapper which re-exports the runtime package, to ensure that @netlify/build doesn't error out when the runtime hasn't been built yet. The problem is that because the wrapper isn't called @netlify/plugin-nextjs, the CLI attempts to auto-install the runtime, leading to errors from double installs. The same problem occurs when running demo sites locally.

This PR changes the demo sites to specify the runtime package as @netlify/plugin-nextjs. This is correctly resolved in the monorepo so that it loads the local version. However we still need to work around the need to compile the runtime. The wrokaround here is two-fold. First we change the entrypoint in the runtime from the compiled lib/index.js, to a static file in the root index.js which re-exports lib/index.js. This means that when build starts, it is able to resolve the entrypoint file and not throw an error. We keep the plugin-wrapper plugin, but make it empty and just use it to ensure that npm install is run, which in turn builds the runtime.

Test plan

1. Ensure the demo sites build

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🧪 Once merged, make sure to update the version if needed and that it was published correctly.