Fix issue OpenFlipper-Free#176, Qt UIC include directories.
Single configuration generators on Windows (e.g. nmake) didn't get the correct include path for autogenerated headers from .ui files.
Multi-configuration generators (e.g. MSVC) only worked in an incomplete subset of build types.
While AUTOUIC automatically sets include directories for the target, these only seem to be PRIVATE include dirs, leading to failure when trying to use them from other projects than where the .ui file lives.