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>

pkgs/tools/package-management/nix-universal-prefetch/default.nix

@@ -0,0 +1,32 @@
+{ lib, stdenv
+, fetchFromGitHub
+, ruby
+}:
+
+# No gems used, so mkDerivation is fine.
+stdenv.mkDerivation rec {
+  pname = "nix-universal-prefetch";
+  version = "0.4.0";
+
+  src = fetchFromGitHub {
+    owner = "samueldr";
+    repo = "nix-universal-prefetch";
+    rev = "v${version}";
+    sha256 = "sha256-HGn4qHWqpUwlS3yQrD3j5oH0yOlphsoSPD2vkyyRv+0=";
+  };
+
+  installPhase = ''
+    mkdir -pv $out/bin
+    cp nix-universal-prefetch $out/bin/nix-universal-prefetch
+    substituteInPlace "$out/bin/nix-universal-prefetch" \
+      --replace "/usr/bin/env nix-shell" "${ruby}/bin/ruby"
+  '';
+
+  meta = with lib; {
+    description = "Uses nixpkgs fetchers to figure out hashes";
+    homepage = "https://github.com/samueldr/nix-universal-prefetch";
+    license = licenses.mit;
+    maintainers = with maintainers; [ samueldr ];
+    platforms = platforms.linux ++ platforms.darwin;
+  };
+}