I don't know what can be the error because if I compare this build with a build that passed earlier, the only change I can find is that now cygwin install unzip to be able to also build VMMaker.
See diff here: https://www.diffchecker.com/sAQ7WlFr At the left the build from `Merge pull request #241 from OpenSmalltalk/sista_lowcode_clang_again` At the right the build from `Pull request #242 - Refactor cygwin installation for appveyor`