Fix compilation on MacOS Catalina

[riordant]

Fixed upstream on Bitcoin (bitcoin#16387)

[UdjinM6]

Thanks for submitting. However this looks like an incomplete backport of at least bitcoin#14123 and bitcoin#16720. We try to avoid patching like that and prefer clean backports (ideally without skipping any intermediary PRs unless they are focused on things like segwit, rbf etc.) because otherwise we'd have to resolve lots of merge conflicts in the future and it becomes a huge mess very quickly.

So yes, it's a good idea to backport fixes and make it compilable on Catalina but not this way.

nACK

PS. if you decide to change this to a "clean" version I described above, pls also rebase it on top of develop (and select correct branch in Github UI) because master is a stable branch in Dash Core (unlike in Bitcoin Core) and all fixes should go into develop only.

[UdjinM6]

Superseded by #3463