[llvm] [LLVMABI] Implement the ABI Typesystem (PR #158329)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Thinking about this again, I think it would be a good idea to also add the CMakeLists.txt and a dummy Types.cpp file that just includes this Types.h and does nothing else for now. Otherwise the build system is not going to check whether this header even compiles successfully.

https://github.com/llvm/llvm-project/pull/158329