Test on FreeBSD is failing due to `tar entry kind 'GNUSparse' is not supported`

Unfortunately, when trying to upgrade our FreeBSD runner to v15 in #4750, we have hit another regression on FreeBSD (https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=286618, https://github.com/alexcrichton/tar-rs/issues/295):

  stderr:
  ====
  info: syncing channel updates for stable-x86_64-unknown-freebsd
  info: latest update on 2024-05-01 for version 1.78.0 (hash-stable-1.78.0)
  info: downloading 4 components
  error: failed to extract package: tar entry kind 'GNUSparse' is not supported
  
  ====
  
  
  thread 'suite::cli_v2::update_removed_component_toolchain' (112036) panicked at src/test/clitools.rs:197:9:
  assertion `left == right` failed
    left: Some(1)
   right: Some(0)

https://github.com/rust-lang/rustup/actions/runs/23116207400/job/67142055466?pr=4750