Stronger MacOS Sandbox with FSKit

Description of the feature request:

@thesayyn has been studying the new https://developer.apple.com/documentation/FSKit API introduced in recent versions of MacOS. We believe this could allow a sandbox implementation that's both fast and isolated, in the sense that it avoids common sandbox escaping by following symlinks.

Background:

• Current implementation is substantially slower than local spawn: https://github.com/bazelbuild/bazel/issues/8230 from 2019
• NodeJS tooling always follows symlinks, even when implemented in Go or Rust. Thus the new Go implementation of the TypeScript type-checker can't run in a Bazel sandbox, along with ESbuild, SWC, OXC, and so on. https://github.com/aspect-build/rules_js/issues?q=is%3Aissue%20state%3Aopen%20sandbox lists some of the issues
• The docker strategy gives a stronger isolation but is impractical since it doesn't re-use containers.
• Sahin has some experiments at https://github.com/thesayyn/sandboxfs

Alternatives:

• Replace eager symlink creation with an on-demand userland filesystem
• If cross-device hardlinks were permitted, it might help. The kernel security system might need changes.
• MacFUSE has a FSkit implementation now, but you have to reduce secure boot.
• bb-clientd uses an NFS approach but it's brittle (@jsharpe)

Which category does this issue belong to?

Action Spawns