libunistring: fix build and enable tests on darwin

pkgs/development/libraries/libunistring/default.nix

@@ -9,21 +9,17 @@ stdenv.mkDerivation rec {
     sha256 = "1x9wnpzg7vxyjpnzab6vw0afbcijfbd57qrrkqrppynh0nyz54mp";
   };
 
-  patches = stdenv.lib.optionals stdenv.isDarwin [ ./clang.patch stdenv.secure-format-patch ];
-
   outputs = [ "out" "dev" "info" "doc" ];
 
   propagatedBuildInputs = stdenv.lib.optional (!stdenv.isLinux) libiconv;
 
-  enableParallelBuilding = false;
-
   configureFlags = [
     "--with-libiconv-prefix=${libiconv}"
   ];
 
-  # XXX: There are test failures on non-GNU systems, see
-  # http://lists.gnu.org/archive/html/bug-libunistring/2010-02/msg00004.html .
-  doCheck = (stdenv ? glibc) && (stdenv.hostPlatform == stdenv.buildPlatform);
+  doCheck = true;
+
+  enableParallelBuilding = true;
 
   meta = {
     homepage = http://www.gnu.org/software/libunistring/;