ghcjs: mark build broken

pkgs/development/compilers/ghcjs/base.nix

···
   license = stdenv.lib.licenses.bsd3;
   platforms = ghc.meta.platforms;
   maintainers = with stdenv.lib.maintainers; [ jwiegley cstrahan dmjio ];
+  hydraPlatforms = if broken then [] else ghc.meta.platforms;
   inherit broken;
 })

pkgs/development/compilers/ghcjs/default.nix

···
 
 bootPkgs.callPackage ./base.nix {
   inherit bootPkgs cabal-install;
+  broken = true;  # https://hydra.nixos.org/build/70552553
 }