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

[James Henderson via llvm-commits]

jh7370 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.

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