[llvm] [Allocator] Keep bump pointer at a minimum alignment (PR #203718)

[Alexis Engelke via llvm-commits]

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

LGTM. Sorry for the delay (moving, no internet at home, locked out of my office due to $security-bureaucracy...).

https://github.com/llvm/llvm-project/pull/203718