OMFG - I’ve wasted 2 days of my life, and this post probably saved me yet a few more days; THANK YOU. Building locally was fine, building on a build machine named builder (hence workspace in /home/builder/...) was failing as mentioned in the OP’s post.
Whoever wrote logic based on substring match inside a full path against build should be shot. Wackiness on their part assuming that artifacts won’t be living in a path with the word build in it. me facepalms