Pure CMake install not installing most project assets

[alerque]

Following discussion in #151 I've been trying to switch Arch Linux packaging from Meson to CMake. With v1.3.0 sources I'm getting surprising results from cmake --install. I'm trying to use the pure CMake backend (not the Ninja backend used in the Makefile.

It's "working" as in running sucessfully, but the only thing it ends up installing is

a) all the sdbuss-c++ stuff (addressed in #151)
b) /usr/bin/hyprland-share-picker

Missing is the systemd service file, the dbus desktop file, the package config file, the config file, and the actual portal. Those things seem to be built with cmake --build,, but not installed using DESTDIR="..." cmake --install <build_dir>.