Update llvm11 to version 11.0.1 / rev 18 via SR 1087215
    
    https://build.opensuse.org/request/show/1087215
    by user aaronpuchert + dimstar_suse
    - Always use ld.bfd for stage 1, and on Tumbleweed use lld for
      stage 2 where we use ThinLTO and where it's supported, otherwise
      ld.bfd (on s390x with LLVMgold.so), on ppc64 we disable ThinLTO
      for now. On Leap/SLE we continue using gold for ThinLTO because
      lld and ld.bfd don't quite work there yet. (Combining fixes for
      boo#1181621 and boo#1210688.)
    - Using ld.bfd on s390x exposed an issue with the existing
      llvm_build_tablegen_component_as_shared_library.patch: linking
      llvm-tblgen with libLLVM.so means we also have to link libraries
      used for that (like LLVMTableGenGlobalISel) with libLLVM.so.
    - Rewrite summary and description for llvm-gold to point out that
      it can also be used with ld.bfd, recommend with binutils.
    - Ignore some test failures on s390x.