While merging #3452 (internal MSVC-PR-457627), I had to disable the Clang/LLVM UBSan configurations for the internal test harness, as they fail to link (with linker errors about support machinery). We use Clang/LLVM via an internally captured "NuGet package" with a subset of binaries (but most of the support libs, AFAIK) to avoid excessive space consumption. At the time, I am unsure why UBSan doesn't work in the internal environment. It could be that we need to add more libs to the NuGet package, or it could be due to PATH ordering issues where we're mixing up MSVC and Clang/LLVM's support libs.

Thanks to @zacklj89 for reminding me to file this followup issue instead of being a bad kitty 😼 and silently working around it forever.