Add find module for Google's libphonenumber
Summary:
This is currently in use by plasma-phone-components, but will also be
needed by KItinerary.
Reviewers: Build System, Frameworks, cgiboudeaux
Reviewed By: cgiboudeaux
Subscribers: cgiboudeaux, kde-frameworks-devel, kde-buildsystem
Tags: Frameworks, Build System
Differential Revision: https://phabricator.kde.org/D16954