Now I think I really have broken the build. The file llvm/test/TableGen/BitsInit.td ended up with an occurrence of '..' rather than '...'. But when I look at the commit I see the line with '...'. I'm not yet too clever with git. Could someone give me a hand?
http://lab.llvm.org:8011/builders/clang-cmake-x86_64-sde-avx512-linux/builds/44547