XTOS_VERSION and CRAYOS_VERSION are no longer viable to use in Modules/Platform/CrayLinuxEnvironment.cmake
In Modules/Platform/CrayLinuxEnvironment.cmake, two environment variables are checked for to verify the CLE OS Version. These variables are no longer viable to use because the modules that provide them and the CLE OS itself are released separately. This will start to be apparent on newer systems.
There are several candidate files that could be used in a directory on the system in their place, however.
This directory exists for both CLE 5 and CLE 6 and has files for both.
Please let me know how you'd like to proceed.