TODO: write a propper error handler based on LLVM-extract

[ZuseZ4]

Throwing 200k LoC+ errors at users isn't productive.
Write an error handler that uses llvm-extract (or better the API equivalent https://llvm.org/doxygen/classllvm_1_1ExtractGVPass.html#a334e522b8b7f2944121de406ab0875fb) to write breaking input functions into files, so we can try to differentiate all functions first and abort compilation with a rustc level error when we wrote at least one error to disk.
This avoids the huge LLVM-IR modules from Rust's std library.

[ZuseZ4]

closed by #134