uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/lib/make-system-tarball.nix

@@ -0,0 +1,56 @@
+{ stdenv, closureInfo, pixz
+
+, # The file name of the resulting tarball
+  fileName ? "nixos-system-${stdenv.hostPlatform.system}"
+
+, # The files and directories to be placed in the tarball.
+  # This is a list of attribute sets {source, target} where `source'
+  # is the file system object (regular file or directory) to be
+  # grafted in the file system at path `target'.
+  contents
+
+, # In addition to `contents', the closure of the store paths listed
+  # in `packages' are also placed in the Nix store of the tarball.  This is
+  # a list of attribute sets {object, symlink} where `object' if a
+  # store path whose closure will be copied, and `symlink' is a
+  # symlink to `object' that will be added to the tarball.
+  storeContents ? []
+
+  # Extra commands to be executed before archiving files
+, extraCommands ? ""
+
+  # Extra tar arguments
+, extraArgs ? ""
+  # Command used for compression
+, compressCommand ? "pixz"
+  # Extension for the compressed tarball
+, compressionExtension ? ".xz"
+  # extra inputs, like the compressor to use
+, extraInputs ? [ pixz ]
+}:
+
+let
+  symlinks = map (x: x.symlink) storeContents;
+  objects = map (x: x.object) storeContents;
+in
+
+stdenv.mkDerivation {
+  name = "tarball";
+  builder = ./make-system-tarball.sh;
+  nativeBuildInputs = extraInputs;
+
+  inherit fileName extraArgs extraCommands compressCommand;
+
+  # !!! should use XML.
+  sources = map (x: x.source) contents;
+  targets = map (x: x.target) contents;
+
+  # !!! should use XML.
+  inherit symlinks objects;
+
+  closureInfo = closureInfo {
+    rootPaths = objects;
+  };
+
+  extension = compressionExtension;
+}