Users should still be able to build applications with qmake against the CMake built Qt.
As a consequence we should also be able to build other Qt modules using qmake against a qtbase built with CMake.
This would also allow gradual migration from qmake to CMake on a per-module basis.
This will probably mean the following:
1) Generate .pri and .prl files for each module built
2) Generate an appropriate qt.conf file that lives alongside qmake, so that cross builds work.