MacOS build is up! Let me know if it works for you.
It mostly does! The mouse pointer gets captured properly, so that's solved... but the doors are the wrong color (yellow instead of red, I don't think I switched the palette?), the viewmodel for the weapon doesn't draw and the enemies are invisible but still shoot (the bullets are visible). Thanks for giving it a shot!
Also PRO TIP: if you pull up the Build Settings window, you can pick "Mac OS X" in the Target Platform dropdown (if you installed support when you installed Unity). That would save you the headache of the round trip to Cloud Builds. :)