[Development] Cross compiling Qt 5

[Peter Kümmel]

Qt could be compiled native or cross for a system 
different to the system on which Qt is build.

But this is not how mkspecs/ is organized:

linux-*        native
win32-*        native
wince*         cross
unsupported/*  cross and native
device/*       cross

also configure supports different options:
  -xplatform
  -device
  -device-options
  -sysroot

In short, it is a mess.


Couldn't we cleanup this by only having native specs
in 'mkspecs' and cross specs in 'mkspecs/target'.

A more configure like option would be 'target',
not 'xplatform' or 'device':

http://airs.com/ian/configure/configure_5.html
   When building cross compilation tools, 
   there are two different systems involved: 
   the system on which the tools will run, 
   and the system for which the tools generate code.
   - The system on which the tools will run is called the host system.
   - The system for which the tools generate code is called the target system.

Therefore I propose to cleanup this before the 5.0 release.


AFAIK host != "system on which configure runs" is not supported by Qt, 
so we only need 'target' based options.

We need at least these two options:
  1. specify mkspec name
  2. specify toolchain prefix

maybe also ( http://labs.qt.nokia.com/2012/04/13/cross-compiling-qt-for-the-masses/ )
  3. sysroot
  4. additional options


Here a proposal:
  1. -target-mkspec  : specify mkspec name
  2. -target         : specify toolchain prefix
  3. isn't sysroot specified by the toolchain compiler? 
  4. not needed


Or are we already in the "wait for 5 + N mode"?

Peter