SHELL_RC_SNIPPET doesn't work in zsh
FirstRun script can modify shell startup scripts such as ~/.bashrc and ~/.zshrc. But the script it appends is highly specific to bash shell: completion in zsh is way different and incompatible.
## Register autocomplete function
complete -o nospace -F _comp-kdesrc-run kdesrc-run
zsh: command not found: complete
Besides, there are better way to provide completion support, like installing global autoloaded functions. Has anyone tried make packages out of kdesrc-build itself? At least there's something in AUR, so it might as well install correct completion scripts, right?