bluez-qt: Overwrite UDEV_RULES_INSTALL_DIR

Summary:
Overwrite the UDEV_RULES_INSTALL_DIR variable to ensure that the udev rules file is installed in the correct directory.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

Reviewers: vkrause

Reviewed By: vkrause

Differential Revision: https://phabricator.kde.org/D22754