In order to support modern macOS features like Dark Mode, we need to use Qt 5.15, which requires macOS 10.13. However, we still want to support macOS 10.10 as well, for which we need to use Qt 5.9. Build separate macOS packages for these use cases.
Fixes: #21606 (closed)
Issue: #20825 (closed)
Backport: release:HEAD~1^2