Fix: Missing dependencies for kwin autotests

guix (like nix) used a separate prefix for each package. Thus the header
files for
qtdeclarative are in /gnu/store/…-qtdeclarative-5.9.1/include/qt5/ while
the ones for
qtbase are in /gnu/store/…-base-5.9.1/include/qt5/. This means that
*each* dependency's include directory must be specified. This is in
contrast to a "normal" Unix-system, where all includes end up in
/usr/include/qt5 and missing to defined some include-dependencies does
often not raise an error.

Differential Revision: https://phabricator.kde.org/D8112