Alex Samorukov commented:
I would not recommend to install anything on the runner itself - this way it would be not possible to get reproducible builds, get bugs related to SDK version (very common for macos!) or use specific version of the xcode.
Solution could be virtualization (what is kind of expensive in terms of hw cost + i think we will need to get vmware license, as vbox is very bad on that) or sandboxing, see https://github.com/jmmv/sandboxctl. I am planning to play with it.