ENOLCK when sync=nfs

[asomers]

I attempted to use vmactions/freebsd-vm, which makes use of anyvm.py, to run a Rust job in a FreeBSD VM. But it failed with this error:

    Updating crates.io index
error: failed to write /home/runner/work/nix/nix/Cargo.lock

Caused by:
  failed to lock file: /home/runner/work/nix/nix/Cargo.lock

Caused by:
  No locks available (os error 77)

That means that fcntl(2) or flock(2) failed. There are several possible solutions

• Mount with NFSv4 instead of v2 or v3
• Run rpc.lockd on both host and guest
• Mount with -o nolockd (might work on FreeBSD only)