[llvm-branch-commits] [CIR] Add options to emit ClangIR and enable the ClangIR pipeline (PR #89030)

[Nathan Lanza via llvm-branch-commits]

https://github.com/lanza created https://github.com/llvm/llvm-project/pull/89030

Introduce just the option definitions and support for their existance at
a few different points in the frontend. This will be followed soon by
functionality that uses it.