I think High Sierra doesn't have the Swift 5 libraries. You might need to install them from the Apple website first: https://support.apple.com/kb/DL1998?locale=

I think High Sierra doesn't have the Swift 5 libraries. You might need to install them from the Apple website first: https://support.apple.com/kb/DL1998?locale=en_US https://support.apple.com/kb/DL1998?locale=en_US I have that information in the troubleshooting section on Github but I'll have to update the official website to also include that.