How2: Swift 4 TF
error: Swift does not support the SDK 'MacOSX10.14.sdk'
You have most probably downloaded the newer toolchain version of the
swift4TF (e.g. Xcode 11 from https://github.com/tensorflow/swift/blob/master/Installation.md)
FIX
Download the Xcode 10 toolchain version, and use that one