Callback that may override the data layout of an imported bitcode module.
Declared in <llvm/Bitcode/BitcodeReader.h>
typedef std::function<std::optional<std::string>(StringRef, StringRef)> DataLayoutCallbackFuncTy;The first argument is the target triple. The second is the data layout string from the input, or a default. That input layout is used if the callback returns std::nullopt.