[llvm] [ADT] Require base equality in indexed_accessor_iterator::operator==() (PR #107856)

[David Blaikie via llvm-commits]

https://github.com/dwblaikie approved this pull request.

Worth a go - you've run check-all with this & verified to a reasonable degree that there aren't existing violations of this invariant?

https://github.com/llvm/llvm-project/pull/107856