[llvm] [llvm-objcopy] Fix file offsets when PT_INTERP/PT_LOAD offsets are equal (PR #80562)

[Steven Johnson via llvm-commits]

steven-johnson wrote:

I very much doubt that we are using `llvm-objcopy` in this code path, so it may be that bisect is lying to me here, combined with some odd bad luck in reproing. I'll do some more debugging locally.

https://github.com/llvm/llvm-project/pull/80562