Revert "coreutils: Update to 8.20"

This reverts commit 1620307488.

8.20 doesn't build on x86_64-darwin.

http://hydra.nixos.org/build/3435174

pkgs/tools/misc/coreutils/default.nix

@@ -7,11 +7,11 @@ assert aclSupport -> acl != null;
 assert selinuxSupport -> libselinux != null && libsepol != null;
 
 stdenv.mkDerivation rec {
-  name = "coreutils-8.20";
+  name = "coreutils-8.19";
 
   src = fetchurl {
     url = "mirror://gnu/coreutils/${name}.tar.xz";
-    sha256 = "1cly97xdy3v4nbbx631k43smqw0nnpn651kkprs0yyl2cj3pkjyv";
+    sha256 = "1rx9x3fp848w4nny7irdkcpkan9fcx24d99v5dkwgkyq7wc76f5d";
   };
 
   buildNativeInputs = [ perl ];
@@ -20,7 +20,7 @@ stdenv.mkDerivation rec {
     ++ stdenv.lib.optional selinuxSupport libselinux
     ++ stdenv.lib.optional selinuxSupport libsepol;
 
-  crossAttrs = {
+  crossAttrs = ({
     buildInputs = [ gmp ]
       ++ stdenv.lib.optional aclSupport acl.hostDrv
       ++ stdenv.lib.optional selinuxSupport libselinux.hostDrv
@@ -32,7 +32,14 @@ stdenv.mkDerivation rec {
     # I don't know why it is not properly detected cross building with glibc.
     configureFlags = [ "fu_cv_sys_stat_statfs2_bsize=yes" ];
     doCheck = false;
-  };
+  }
+
+  //
+
+  # XXX: Temporary workaround to allow GNU/Hurd builds with newer libcs.
+  (stdenv.lib.optionalAttrs (stdenv.cross.config == "i586-pc-gnu") {
+    patches = [ ./gets-undeclared.patch ];
+  }));
 
   # The tests are known broken on Cygwin
   # (http://thread.gmane.org/gmane.comp.gnu.core-utils.bugs/19025),