[Development] QT5 Configure has windows specific code

[Mark Brand]

> I am trying to build configure in QT5 on linux host. But it seems like 
> there is windows specific code in some of its files 
> like configureapp.cpp and environment.cpp. Is there any solution to this? 

Yes, for cross-compiling Qt on a linux host for MinGW, the configure 
script can be used, at least for some combinations of options. This is 
how MXE  http://mxe.cc/ builds both Qt 4 and Qt 5. I recommend using the 
development version (i.e., master branch). Even if MXE's Qt 
configuration isn't exactly what you want, it's probably at least a good 
place to start.

Mark