Build fails due to CMake 3.28 identifying Cray PE as 'CrayClang'

[cdm-work]

Attempting to build Charm on a system with CMake version 3.28.3, with the Cray programming environment, the cmake .. command fails to configure the environment. It reports this in the output:

...
-- Found OpenMP_C: -openmp (found version "5.1") 
-- Found OpenMP_CXX: -openmp (found version "5.1") 
-- Found OpenMP: TRUE (found version "5.1")  
CMake Error at CMakeLists.txt:62 (message):
   Unknown compiler CrayClang

-- Configuring incomplete, errors occurred!

Reviewing the CMake documentation, it would appear that this new detection was added with CMake 3.28. And it's pretty clear in the CMakeLists.txt that it does not expect this value for CMAKE_CXX_COMPILER_ID.

The attached patch file seems to resolve the issue. patch-CMakeLists.txt