Fix symlink issues by using useHostFilesystem

[sejas]

Related issues

• Fixes https://github.com/Automattic/dotcom-forge/issues/10566

Proposed Changes

• I suggest using useHostFilesystem instead of mounting each symlink directory.

Testing Instructions

1. Have a Studio site where Yoast SEO is not already installed
2. Download Yoast SEO and extract it to ~/wordpress-seo
3. In your site's wp-content/plugins directory, run ln -s ../../../../wordpress-seo (you'll need at least four levels of ../, but the symlink also needs to resolve correctly)
4. Start the Studio site
5. Navigate to /wp-admin/plugins.php
6. Observe the Yoast SEO plugin there
7. Activate it
8. Observe the site is running correctly as always

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[fredrikekelund]

This fixed the problem for me on Mac, but it doesn't work at all on Windows (I can't start sites—even without symlinks). I get the following error on Windows:

 Error: EPERM: operation not permitted, lstat 'C:\Config.Msi'

[fredrikekelund]

Looking at the useHostFilesystem source, it seems possible that it would work on Windows, but we'd need to start by capturing errors thrown from lstatSync.

[wojtekn]

Nice, simplifying symlink handling that way looks promising.

[sejas]

I'm closing this PR to find the real issue in Playground/Emscripten. I'll work on it later this week and It will take more time than this solution, but it should be a more conservative solution that fixes the root cause.