Not to mention that the existing "make install" process takes care of installing icons and applications files that will work with standard linux XDG desktops to populate menus and such.
It should be trivial for someone to modify the cmake files to install these files in locations where Haiku expects them to be.
I have no problem helping with compilation issues, but I'm not really interested in learning how to package applications for Haiku (or any other distro for that matter). That's someone else's job.
Happy to help package maintainers if there's something about the Sigil build process that makes it impossible (or very difficult) to package, but I'm not a distro package maintainer. Nor do I desire to be.