Revert "fixup! WIP: Hydra builds."

This reverts commit cf0ac91.

bazel.nix

@@ -182,6 +182,19 @@ let
           echo 'common --remote_http_cache=http://34.243.81.23:80'
         ) >> $BAZELRC_LOCAL
       fi
+
+      # link the tools bazel will import to predictable locations
+      mkdir -p tools
+      ln -nfs ${ghc} ./tools/ghc
+      ln -nfs ${happy} ./tools/happy
+      ln -nfs ${alex} ./tools/alex
+      ln -nfs ${hlintScript} ./tools/hlint
+      ln -nfs ${stylishHaskellScript} ./tools/stylish-haskell
+      ln -nfs ${shellcheckScript} ./tools/shellcheck
+      ln -nfs ${purescript} ./tools/purescript
+      mkdir -p yarn-nix/bin
+      ln -nfs ${nodejs} ./node-nix
+      ln -nfs ${yarn}/bin/yarn ./yarn-nix/bin/yarn.js
     '';
   };