[CMake] Auto re-configuring until cache stops changing

[David Doria]

Lately I've been making a class full of students use CMake. Without
exception, I've had to explain why you have to configure twice to
build VTK. I imagine they are a representative sample of the "Level 0"
CMake user - they just want the project they are trying to build "to
work" with default options, etc.

(The explanation is here:
http://www.cmake.org/cmake/help/runningcmake.html
under "Why do I have to edit the cache more than once for some projects?"
if anyone reading this is wondering)

Since CMake knows if the cache has changed (it doesn't let you
generate if it has), when why can't there be a button called "Setup
project with default options" or "Really configure + generate" that
configures as many times as  necessary and generates all in one step?
I bet this button would get the most clicks by the general population.

Just a suggestion - any thoughts?

Thanks,

David