Yarn 2 needs proper support in builds

[PizzaFox]

Currently Netlify does a few things that are bad for Yarn 2 users:

• Caches the node_modules directory regardless of the configured Yarn cacheFolder
• Uses the deprecated cache-folder option, which will throw a YN0050 error

The most annoying consequence of this is that every time one of my Yarn 2 projects is built it downloads 2 copies of the dependencies, every single build (one from Netlify cache, one from Yarn 2). This results in much longer builds as there is now effectively 0 caching of dependencies.

The Netlify build image should be updated to better handle projects that use Yarn 2.

[jen]

Hey @PizzaFox,
Thanks for this feature request. We have several open issues about this on the build-image repo- I believe this comment links to all of them:

Support for caching yarn workspaces' node_modules

Please feel free to chime in there and/or follow along for updates.