project() call should always come AFTER cmake_minimum_required(). This caused various hard-to-debug issues when searching for packages.
Newer CMake versions complain that compatibility is broken with v2.6
https://cgit.freedesktop.org/mesa/glu/
The library is stable (it should be, since it is in use since 1994),
but it is not thread safe: Its callbacks do not receive any pointer
to a context.