Merge pull request #136640 from NixOS/backport-136629-to-release-21.05

[Backport release-21.05] llvmPackages_13.compiler-rt: Mark as broken on Aarch64

pkgs/development/compilers/llvm/13/compiler-rt/default.nix

@@ -110,5 +110,7 @@ stdenv.mkDerivation {
     # "All of the code in the compiler-rt project is dual licensed under the MIT
     # license and the UIUC License (a BSD-like license)":
     license = with lib.licenses; [ mit ncsa ];
+    # TODO/FIXME: Build fails on Hydra:
+    broken = stdenv.isAarch64;
   };
 }