`fir.local` ops are not supposed to have any uses at this point (i.e. during lowering to LLVM). In case of serialization, the `fir.do_concurrent` users are expected to have been lowered to `fir.do_loop` nests. In case of parallelization, the `fir.do_concurrent` users are expected to have been lowered to the target parallel model (e.g. OpenMP). This hopefully resolved a build issue introduced by https://github.com/llvm/llvm-project/pull/142567 (see for example: https://lab.llvm.org/buildbot/#/builders/199/builds/4009).