[Qt-creator] CMake builds vs qmake builds

[Coda Highland]

> Traditionally, qmake was much better at this than it is now. Or at least
> it seemed to be.

It's purely an issue of SEEMING to be. In-tree builds do work for a
good number of projects, but you start bumping into problems -- for
example, switching between debug and release and getting the object
files mixed up. Shadow builds are safer in general.

/s/ Adam