libatomic-ops FTBFS on arm64ilp32 arch. This trival patch fixes that.

It might be better to refactor the code to check for ILP32 on all
64-bit arches that support it rather than this per-arch fix, but I
don't know enough about the codebase to be sure if that is a good
idea. This is a safe, minimal patch.

Sorry for the delay on this

As you're the expert, could you submit this as a pull request on

https://github.com/ivmai/libatomic_ops

When it is accepted upstream I'll happily include it as a debian patch
until it makes it into a release, but I'm very hesitant to do that without
upstream review first.  Even trivial things that break atomicity would be
bad

Thanks,