https://aws.amazon.com/blogs/aws/new-use-mac-instances-to-build-test-macos-ios-ipados-tvos-and-watchos-apps/
These aren't VMs as per the norm, but bare metal instances. Intel-based instances are available today, with Apple Silicon M1 coming in 2021. I imagine this will further increase the need for macOS package managers like MacPorts and Homebrew.
