Build README instructions appear outdated. (Dead URL for XCode)
"1. Download the Xcode 11.3.1 to obtain the OSX 10.15 SDK (obtainable from Apple Developer Downloads [here](https://download.developer.apple.com/Developer_Tools/ Xcode_11.3.1/Xcode_11.3.1.xip))"
That XCode is no longer available. Do you just want to be pointing to https://download.developer.apple.com/Developer_Tools and telling us to get the latest? Especially now that Monterey is out.