Support starting the rules_dialog from build dir
Summary:
As with all libexec executables we first need to test whether the binary
is available in the application's directory and start this, otherwise
the system wide installed one.
See: https://community.kde.org/Guidelines_and_HOWTOs/Making_apps_run_uninstalled
Reviewers: KWin
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D16765