I am responsible for one of the buildbots that failed (https://lab.llvm.org/buildbot/#/builders/172). If you don't have access to a Windows machine to reproduce the problem, I could help.
@Meinersbur Thanks, I'd appreciate it. It looked easy enough to fix, but if you could give it a pre-test then for your convenience I put it here: https://github.com/nhaehnle/llvm-project/tree/managedstatic-dynamiclibrary
git fetch email@example.com:nhaehnle/llvm-project.git managedstatic-dynamiclibrary && git switch -d FETCH_HEAD