It shouldn't. Usually FreeCAD's CMake will look for these, that point to a XYZcongig.cmake file. Depending on the version of the package this may or may not work to set all the other XYZ variables. If it is doesn't work FreeCAD tries to find them another way, sometimes the user must supply them.
Strange, I would expect errors for the Debug builds due to the Libpack, but Release should work (I use this Libpack for the Win daily builds)