Recent versions of cmake complain about it:

<<
  CMake Deprecation Warning at CMakeLists.txt:1 (cmake_minimum_required):
  Compatibility with CMake < 2.8.12 will be removed from a future version of
  CMake.
>>

We don't require anything from version 2.8.5, and version 2.8.12 was
released in 2011, so it is very unlikely that anyone still uses 2.8.5.