squashfs: support darwin

pkgs/tools/filesystems/squashfs/default.nix

@@ -22,7 +22,7 @@ stdenv.mkDerivation rec {
     ./0001-If-SOURCE_DATE_EPOCH-is-set-override-timestamps-with.patch
     ./0002-If-SOURCE_DATE_EPOCH-is-set-also-clamp-content-times.patch
     ./0003-remove-frag-deflator-thread.patch
-  ];
+  ] ++ stdenv.lib.optional stdenv.isDarwin ./darwin.patch;
 
   buildInputs = [ zlib xz ]
     ++ stdenv.lib.optional lz4Support lz4;
@@ -37,7 +37,7 @@ stdenv.mkDerivation rec {
   meta = {
     homepage = http://squashfs.sourceforge.net/;
     description = "Tool for creating and unpacking squashfs filesystems";
-    platforms = stdenv.lib.platforms.linux;
+    platforms = stdenv.lib.platforms.unix;
     license = stdenv.lib.licenses.gpl2Plus;
     maintainers = with stdenv.lib.maintainers; [ ruuda ];
   };