message: CallSite.h is missing in LLVM 11, but ONLY AbstractCallSite.h
diff: #include "llvm/CodeGen/IntrinsicLowering.h"
  #include "llvm/CodeGen/Passes.h"
  #include "llvm/IR/CFG.h"
  -#include "llvm/IR/CallSite.h"
  +#include "llvm/IR/AbstractCallSite.h"
  #include "llvm/IR/CallingConv.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DerivedTypes.h"
  