[llvm] adds conversion functions for EI_OSABI in elf (PR #89280)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

I feel like some basic unit testing for this should really exist. I'll acknowledge that there's probably not a huge amount of point testing every single OS/OSABI pair, but you could test a few arbitrary cases, plus the "none" and default cases.

https://github.com/llvm/llvm-project/pull/89280