perlPackages.mimeConstruct: only "out" output

http://hydra.nixos.org/build/38074006/nixlog/1

pkgs/top-level/perl-packages.nix

···
       url = "mirror://cpan/authors/id/R/RO/ROSCH/${name}.tar.gz";
       sha256 = "00wk9950i9q6qwp1vdq9xdddgk54lqd0bhcq2hnijh8xnmhvpmsc";
     };
+    outputs = [ "out" ];
     buildInputs = [ ProcWaitStat ];
   };