Update src/libutil/fmt.hh
Update src/libutil/fmt.hh

Co-authored-by: John Ericson <46f1a0bd5592a2f9244ca321b129902a06b53e03@JohnEricson.me>
rycee/nix,NixOS/nix,rycee/nix,NixOS/nix,NixOS/nix,NixOS/nix,rycee/nix,NixOS/nix,rycee/nix,rycee/nix