CMake misidentifies Cray CCE 9.0+
Starting with version 9, Cray CCE now uses a LLVM front-end. CMake is misidentifying this compiler as clang:
% CC --version
Cray clang version 9.0.1.80 (f471f4522afe616d4fed3afeb6a6b16854b00512) (based on LLVM 9.0.0svn)
Target: aarch64-unknown-linux-gnu
Thread model: posix
InstalledDir: /opt/cray/pe/cce/9.0.1.80/cce-clang/aarch64/bin
% cmake ../source
-- The CXX compiler identification is Clang 9.0.0
-- Check for working CXX compiler: /opt/cray/pe/craype/2.6.0/bin/CC
-- Check for working CXX compiler: /opt/cray/pe/craype/2.6.0/bin/CC -- works
...
CMAKE_CXX_COMPILER_ID = Clang
This causes CMake to use incorrect compile flags.