qbspkgconf module provider creates wrong Qt modules when cross compiling

Aloha,

when cross compiling using the qbspkgconfig module provider will lead to Qt modules for the local installed Qt libraries. The qbspkgconfig just uses the qmake binary path from the pkg-config files but ignores the sysroot.
And even if it would take the sysroot into account it would try to probe the wrong qmake!

I would just disable generating Qt modules from the qbspkgconf module provider if sysroot is set. The user can still set the Qt modules provider qmake path manually (which just works fine).