Clarify FIXME in `BinaryCacheStore::addToStoreCommon`
Clarify FIXME in `BinaryCacheStore::addToStoreCommon`

Co-authored-by: Robert Hensing <1ffad3fb1ab24362ef5dcb21f3f88b4b050415ea@users.noreply.github.com>
NixOS/nix,NixOS/nix,NixOS/nix,rycee/nix,rycee/nix,rycee/nix,rycee/nix,NixOS/nix,NixOS/nix,rycee/nix