Since 6295b8e763503644961f9087382f80965b98d466 in llvm-project, one no longer can configure the openmp project entirely standalone, one has to do it through the runtimes directory. However, in practice, this currently leads to no tests being executed at all, as the runtimes build setup doesn't support pointing to an external FileCheck executable - it currently has to be part of a full bootstrapping build.