Allow rootless 'make install' with non-standard CMAKE_INSTALL_PREFIX

Authored by martinkostolny on Feb 18 2018, 5:14 PM.

Description

Allow rootless 'make install' with non-standard CMAKE_INSTALL_PREFIX

Install Qt plugins to standard locations based on CMAKE_INSTALL_PREFIX. A warning cmake message will be shown to user if non-standard CMAKE_INSTALL_PREFIX is used.

Differential Revision: https://phabricator.kde.org/D9975