To build a Raspbian toolchain for Swift 3.0.2 a few things need to be changed in the original guide.
Download the Swift 3.0.2 packages instead of the 3.1.1 ones:
curl -o /tmp/swift-3.0.2-RPi1Zero-RaspbianNov16.tgz https://www.dropbox.com/s/dkrkt9ht1c3hog2/swift-3.0.2-RPi1Zero-RaspbianNov16.tgz
curl -o /tmp/swift-3.0.2-RELEASE-osx.pkg https://swift.org/builds/swift-3.0.2-release/xcode/swift-3.0.2-RELEASE/swift-3.0.2-RELEASE-osx.pkg
Launch the script with these parameters: