[llvm] [Object,ELF] Implement PN_XNUM extension for program headers (PR #162288)

[via llvm-commits]

aokblast wrote:

> I've approved the other PR, but this one is saying there are no conflicts, so "Squash and merge" should just work and it would be better to land it.
> 
> Force pushes also aren't hard-banned, if you need to make one to clean things up, especially once the review has concluded.

Thanks! I just force push and enable auto-merge.  I will close other PR.

https://github.com/llvm/llvm-project/pull/162288