.gitignore: prepend slash to result and source
.gitignore: prepend slash to result and source

so that it matches only in the repository root.

Co-authored-by: Sandro Jäckel <3f1bc63e633623a49b6f9d32f242d8ac8d282b0e@gmail.com>
Co-authored-by: Milan Hauth <9e4dd675045dce5189b008250980ac2104700520@gmail.com>

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs