libspectrum: add darwin build

pkgs/development/libraries/libspectrum/default.nix

@@ -13,12 +13,13 @@ stdenv.mkDerivation rec {
   buildInputs = [ audiofile bzip2 glib libgcrypt zlib ];
 
   enableParallelBuilding = true;
+  doCheck = true;
 
   meta = with lib; {
     homepage = "http://fuse-emulator.sourceforge.net/libspectrum.php";
     description = "ZX Spectrum input and output support library";
     license = licenses.gpl2Plus;
-    platforms = platforms.linux;
+    platforms = platforms.unix;
     maintainers = with maintainers; [ orivej ];
   };
 }