QtModules can't load qmake features from other modules

1. Create a qt5 top-level prefix build
2. Modify a qtquickcontrols2 (or any other module) pro file to load the qmltypes qmake feature.

E.g. Add the following to qtquickcontrols2/src/quickcontrols2/quickcontrols2.pro

load(qmltypes)

This makes sure the qmltypes qmake feature is directly loaded, instead of adding it as CONFIG option which doesn't verify that the feature actually exists.

The qmltypes.prf is part of the qtdeclarative build folder, but when running qmake for qtquickcontrols2 again, it isn't found:

cd <top-level-build-folder>/qtquickcontrols2
make qmake_all

The resulting error is the following:

.../quickcontrols2.pro:14: Cannot find feature qmltypes

If you add the following code to qtquickcontrols2/.qmake.conf:

QMAKEFEATURES+=$$OUT_PWD/../qtdeclarative/mkspecs/features

It can load the feature file and everything works expected.