xrdp-0.9.12 has removed a crucial init file

I have been trying to build the latest version of xrdp and have run into a problem. Previous versions have included a instfiles/xrdp.sh file that is processed by the SlackBuild to become /etc/rc.d/rc.xrdp. I did ask at https://gitter.im/neutrinolabs/xrdp, but got a terse response that the file has been removed in the latest version. Simply adding the missing file to the latest version tarball still causes the SlackBuild to fail, which suggests that support has also been removed from the build system. Perhaps this is an example of projects dropping support for non-systemd distros?

The easiest fix is probably to add a big here string to the SlackBuild to generate the required /etc/rc.d/rc.xrdp, but that seems rather ugly. Any other ideas?