newer CMake complains about cmake_minimum_required(VERSION 2.6.4)

[slayoo]

Cmake 3.20.5 outputs the following warning for PartMC CMakeLists.txt file:

  Compatibility with CMake < 2.8.12 will be removed from a future version of
  CMake.

  Update the VERSION argument <min> value or use a ...<max> suffix to tell
  CMake that the project does not need compatibility with older versions.

There is a comment in the CMakeLists.txt file stating that:

# Require 2.6.4 due to -I/usr/include behavior:
# http://www.cmake.org/Bug/view.php?id=8598
# http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35707
# http://www.cmake.org/Bug/view.php?id=8408

The referenced CMake bug reports are now closed, the gcc one seems to be a WONTFIX.

Any thoughts?

[mwest1066]

I think we should just delete the cmake_minimum_required() line (and the comment lines to the bug trackers). This is all ancient history at this point.

[slayoo]

cmake_minimum_required entry is mandatory https://cmake.org/cmake/help/latest/policy/CMP0000.html#policy:CMP0000

[mwest1066]

cmake_minimum_required entry is mandatory https://cmake.org/cmake/help/latest/policy/CMP0000.html#policy:CMP0000

Haha, excellent point.

Ok, in that case I guess we should change to 2.6.4..3.20.0 (or whatever is the latest version we can test).