[clang] [LifetimeSafety] Add multi-block support to buildOriginFlowChain (PR #204592)

[Yuan Suo via cfe-commits]

suoyuan666 wrote:

> > So, I remove the `StartPoint` parameter to find the `OriginID` correctly.
> 
> Is this still true? Maybe I am looking somewhere wrong but I think you do use that parameter.

Sorry, I made a mistake in my wording here. Let me clarify:

The role of `StartPoint` is no longer the same as before. Previously, the search started from `StartPoint`, but now `StartPoint` is only used to locate the corresponding `BlockID`.

https://github.com/llvm/llvm-project/pull/204592