Apple Silicon build

[mcbarton]

When building on Apple Silicon issues occur when trying to use this repo with xeus-clang-repl

• The Cuda library is loaded
• CppInterOpConfig.cmake.in chooses the wrong file extension when config file is used when building on Apple Silicon

The issue is related to compiler-research/xeus-clang-repl#76

A pull request will be created shortly with a suggested fix the above