[CMake] ExternalProject_Add examples

[Bill Lorensen]

Folks,

I've recently created a number of super builds using CMake's External
Project mechanism. Each external project requires some sort of
download, configuration, build and possibly install. The CMake defines
needed to correctly access the results of the external project vary
significantly. The trickiest part is find the proper download,
configuration and CMake defines.

For example, for the Point Cloud Library (http://pointclouds.org/) I
created these external projects:
VTK - git, cmake, make; VTK_DIR
FLANN - zip, cmake, make install; FLANN_LIBRARY, FLANN_INCUDE_DIR
Eigen - .tar.bz2,; EIGEN_INCLUDE_DIR
Qhull - git, cmake, make;QHULL_LIBRARY,QHULL_INCLUDE_DIR
Boost - .tar.gz, bootstrap.sh, b2; BOOST_ROOT
GTest - .zip, cmake, make; GTEST_ROOT,GTEST_INCLUDE_DIR

Slicer4 has many more.

Should we start collecting sample ExternalProject_Add files for
external projects?

Bill
-- 
Unpaid intern in BillsBasement at noware dot com