rubber: add mainProgram

+1
+1
pkgs/tools/typesetting/rubber/default.nix
··· 50 homepage = "https://gitlab.com/latex-rubber/rubber"; 51 maintainers = with maintainers; [ ttuegel peterhoeg ]; 52 platforms = platforms.unix; 53 }; 54 }
··· 50 homepage = "https://gitlab.com/latex-rubber/rubber"; 51 maintainers = with maintainers; [ ttuegel peterhoeg ]; 52 platforms = platforms.unix; 53 + mainProgram = "rubber"; 54 }; 55 }