[clang] [CIR] Upstream support for FlattenCFG switch and SwitchFlatOp (PR #139154)

[Bruno Cardoso Lopes via cfe-commits]

https://github.com/bcardosolopes commented:

This is also missing a end-to-end test that proves we generate switchflatop if we are coming all the way from source code. There are examples in the incubator on how to check if a pass runs (you can use print-before/after) and the IR for it.

https://github.com/llvm/llvm-project/pull/139154