How to cross-build for a different Linux version (w/ Qt Creator)?

[wysota]

This is very inconvenient. So my question in short is: is there a way to create a toolchain or add-on to the development environment on the new system, so that I can cross-compile there for the old Ubuntu 11.10. I have a second machine where I can run the binary with the old system (that's the actual target machine for the program), but that machine has no development tools whatsoever, plus it is way too slow to compile on there (slow Intel Atom CPU, small memory).

The easiest approach I can think of is to have a chroot of the older system in the newer system and build within that chroot. Have a look at 'schroot'.