[llvm] [DebugInfo] Emit linkage name into DWARF for types for Swift (PR #112802)

[Augusto Noronha via llvm-commits]

augusto2112 wrote:

> so why is this code change needed? Because up until now the mangled name has been put in DW_AT_name, so didn't need LLVM-side support? Or it's been in downstream patches that are being upstreamed? It'd be good to know about what's new/different/etc to add this change now (even if it's just "we've been doing this downstream for a while, and now have time to upstream it" (in which case a bit of info about the original decision that added the functionality would be handy too - but I think you've mostly covered that in this comment, perhaps))

Right, emitting linkage names for types has been downstream for a really long time. Emitting the type linkage names into accelerator tables is new behavior, which is needed to do global searches by linkage names (I'll have another patch soon on the LLDB side to support `FindTypes` optionally looking types up by linkage name). 

https://github.com/llvm/llvm-project/pull/112802