Prevent tempdir from being GC-ed before addToStoreFromDump has renamed it
Prevent tempdir from being GC-ed before addToStoreFromDump has renamed it

This fixes issue 6823 by placing the tempdir used in LocalStore::addToStoreFromDump
outside the Nix store, where automatic GC is no longer a concern.

NixOS/nix,NixOS/nix,NixOS/nix,NixOS/nix,NixOS/nix