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

[Jeremy Morse via llvm-commits]

jmorse wrote:

IMO this is good -- although it directly trades-off debug-info builds against normal builds because it's expanding the size of abbrev-records to five bits instead of four. By eye, it look like between a 0.5% and 1% cost per object file.

I've previously discarded some removing-debug-intrinsics optimisations because of that limitation. I'm fine with saying that we should push through it to enable benefits in non-normal builds. With more effort (and the extra abbrev numberspace) we might recover the cost being added now. Further opinions would be most welcome!

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