Got this build error. Turns out it was due to using Xcode Beta. Found the solution here, which was setting the beta to be default:
https://github.com/PerfectlySoft/Perfect/issues/262#issuecomment-405921471
sudo xcode-select -s /Applications/Xcode-beta.app/Contents/Developer
Posting it here in case someone else has this issue.
Thanks, although I had to change it to:
sudo xcode-select -s /Applications/Xcode.app/Contents/Developer
Thank you. I'd like to also add in case someone else has this issue, that I could not get "export TOOLCHAINS=swift" to change to the latest Swift 5.0 development toolchain until I did this first, so thank you very much.
Thank you!!
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Thanks, although I had to change it to: