Cross-distro and -POSIX packages are easy with Nixstaller. (Note that this pre-dates and is entirely unrelated to NixOS or Nix packages.)
Download Nixstaller from http://nixstaller.sourceforge.net and read the docs there.
Review the sample package templates included in the examples dir.
Generate an empty template dir with genprojdir.sh
Modify the config.lua and run.lua files to suit your needs.
Place your payload(s) into the appropriate folders.
Generate your re-distributable install file with geninstall.sh:
geninstall foo-1.0.0 foo.run