[PATCH] D24084: [CMake] Cleanup libunwind lookup code.

[Logan Chien via cfe-commits]

logan added a comment.

In https://reviews.llvm.org/D24084#532724, @asl wrote:

> I totally agree with Renato. What part of libc++abi requires exactly libunwind's unwind.h, what is the dependency?


To be specific, we need:

- Structure Definition: `_Unwind_Control_Block` (missing from `<unwind.h>` bundled with clang)
- Function Declarations: `_Unwind_GetLanguageSpecificData()`, `_Unwind_GetRegionStart()`,  `_Unwind_{Get,Set}{IP,GR}()`, `_Unwind_{Get,Set}_VRS()`, `_Unwind_RaiseException()`

This is the status quo after `libunwind` was spun off (or splitted) last year.


https://reviews.llvm.org/D24084