fix detection of taglib when compiling for Android

Summary: fix detection of taglib when cross compiling for Android

Test Plan: tagib is properly found instead of the host version of the library

Reviewers: Frameworks, Baloo, bruns

Reviewed By: Baloo, bruns

Subscribers: bruns

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D12341