With Module_vtkRenderingExternal, the tests won't build.
I lost the scroll-back with the error, but effectively, in order to get the tests in Rendering/External/Testing/Cxx
to build, I had to add my GLUT_INCLUDE_DIRECTORY
to the ${vtk-module}CxxTests
target in Rendering/External/Testing/Cxx/CMakeLists.txt
I'm on Ubuntu 14.04, building with g++ 4.8, without a system-wide install of GLUT - instead I was pointing to a local install of freeglut.
I'm using the 7.0.0 tag of VTK, at commit 3ecb4cd9