[CMake] Collaboration of superbuilds with bundled software

[SF Markus Elfring]

Hello,

A variant of the software generation process is described as "superbuild".

Example:
https://cmake.org/Wiki/ParaView/Superbuild

This article mentions the version "2.8.8" as a software dependency for the
tool "CMake". It refers also to the article "Building External Projects with
CMake 2.8" which mentions the version number "2.6.4".
http://www.kitware.com/media/html/BuildingExternalProjectsWithCMake2.8.html

How far can the support for this build approach be also achieved
by older revisions?


I guess that there is some software evolution involved around a command
like "ExternalProject_Add".
https://cmake.org/cmake/help/v3.4/module/ExternalProject.html

* Does this command need to download anything at the beginning?

* Will such a command also work if a needed software component is stored
  together with files in a repository for the main project?

* Would you like to switch between a loadable variant and the bundled revision
  by a configuration option?


Are there any more software development challenges to consider as further
clarification requests might indicate?

* 2015-04-05:
  http://stackoverflow.com/questions/29460893/using-cmake-with-externalproject-add

* 2013-07-03:
  http://stackoverflow.com/questions/17446981/cmake-externalproject-add-and-findpackage

Regards,
Markus