LLVM 22: optimization remarks no longer support "separate" mode

[durin42]

remarks::createRemarkSerializer lost the mode for Separate mode in llvm/llvm-project@dfbd76bda01e. We'll need to work around that if we want to keep -Zremark-dir working (if that's even meaningful at that point, I haven't looked closely.)

[tobias-stadler]

Hi, I'm the author of that LLVM patch. The Separate mode has become superfluous. This distinction was only important for Bitstream remarks, not for YAML remarks. You should be able to safely remove the mode parameter, but there are some considerations about the lifetime of the remarks file and the LLVMRemarkStreamer. I've added some upgrade guidance to the PR (llvm/llvm-project#156715 (comment)). Feel free to ping me, if there are any questions.

[workingjubilee]

Thanks for the additional insight! -Zremark-dir is unstable so whatever reworking it winds up needing is no big deal.