kcminit: Symlink kcminit_start instead of compiling twice
and also reformat CMakeLists in a more consistent way.
Tried. Works. Build log looked like this:
-- Installing: /usr/local/kde/bin/kcminit
-- Set runtime path of "/usr/local/kde/bin/kcminit" to "/usr/local/kde/lib"
-- Installing: /usr/local/kde/bin/kcminit_startup
-- Up-to-date: /usr/local/kde/lib/systemd/user/plasma-kcminit-phase1.service
-- Up-to-date: /usr/local/kde/lib/systemd/user/plasma-kcminit.service