tarfile.cc: Don't change the cwd
tarfile.cc: Don't change the cwd

Nix is multithreaded so it's not safe to change the cwd.

NixOS/nix,rycee/nix,rycee/nix,rycee/nix,ehmry/nix,ehmry/nix,pikajude/nix,pikajude/nix,ehmry/nix,ehmry/nix,ehmry/nix,NixOS/nix,pikajude/nix,NixOS/nix,NixOS/nix,rycee/nix,ehmry/nix,rycee/nix,NixOS/nix