It's amusing to me
The beginning of bullet's cmake is
cmake_minimum_required(VERSION 2.4.3)
And then later including FindPackage( GLU ) which is throwing a warning that it's obsolete and to use opengl instead. (opengl is already used)
In the FindGLU.Cmake module
----------------------
# Use of this file is deprecated, and is here for backwards compatibility with CMake 1.4
# GLU library is now found by FindOpenGL.cmake
#
MESSAGE(STATUS
"WARNING: you are using the obsolete 'GLU' package, please use 'OpenGL' instead")
----------------------
But if the required version is already 2.something, why use a 1.4 findpackage?