[llvm] [LTO] Enable adding custom pass instrumentation callbacks (PR #71268)

[Teresa Johnson via llvm-commits]

teresajohnson wrote:

> Our tool uses the LLVM libraries directly, similar to llvm-lto2 and lld, i.e. we create an LTO object, add InputFiles, run the process, and so on, and this is just one of the transformations the tool does. It is not a script or anything like that.

Can you clarify what you meant by "These are command-line options and their variables are local to the TU. There is no API to access them from other components." Because if you have a tool that is built like llvm-lto2 etc using LLVM libraries, you should be able to parse the internal command line options passed to it. I'm not sure what is TU local about them?

https://github.com/llvm/llvm-project/pull/71268