[llvm] [DebugInfo] Add an specification_of attribute to LLVM DebugInfo (PR #115362)

[David Blaikie via llvm-commits]

dwblaikie wrote:

I'd probably call the attribute just "specification" same as DWARF does?

but also it worries me a bit - the reason we haven't had "specification" in LLVM IR debug info for types so far is that we never have a declaration and a definition of the same type simultaneously - we deduplicate them via the `identifier` if we're merging modules, etc.

So, yeah, maybe a bit more detail on how this works - and maybe it deserves a different name once we look at the details.

https://github.com/llvm/llvm-project/pull/115362