Build servers are a thing, and using a mac as a build node is hilariously complicated and unstable when compared to linux. When my developers push to git the android app is built & tested & uploaded to the store automatically. We also have this working for iOS but it requires a mac in a closet that needs manual maintenance every month or so when apple breaks something again. The linux servers are generally hands-off. Also, android builds are about 10x faster because they run on a machine with 128gb ram and a big cpu which isn't even possible with a mac (and even if it was, I'm sure apple would charge an insane amount for it).