[llvm] [Bitcode][NFC] Add abbrev for FUNC_CODE_DEBUG_LOC (PR #146497)

[David Blaikie via llvm-commits]

dwblaikie wrote:

>  By eye, it look like between a 0.5% and 1% cost per object file [edit: in a normal build].

Huh, that seems like a lot for this one little record... 

I wonder if there's any way to reduce that impact - can't make the abbrev condition on debug info, I guess - too early to know that. The bitcode format does dynamically create abbrevs - but I guess if you don't create explicit ones like this, they aren't shared? Each record has its own abbrev? What if we had a way to add shared abbrevs dynamically?

https://github.com/llvm/llvm-project/pull/146497