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/system/das_watchdog/default.nix

@@ -0,0 +1,34 @@
+{ lib, stdenv, fetchFromGitHub, libgtop, xmessage, which, pkg-config }:
+
+stdenv.mkDerivation {
+  pname = "das_watchdog";
+  version = "unstable-2015-09-12";
+
+  src = fetchFromGitHub {
+    owner = "kmatheussen";
+    repo = "das_watchdog";
+    rev = "5ac0db0b98e5b4e690aca0aa7fb6ec60ceddcb06";
+    sha256 = "sha256-eacUn/gYCEHtHdQf3lBPYvY3kfN3Bik7AolAPpbbwQs=";
+  };
+
+  nativeBuildInputs = [ pkg-config ];
+  buildInputs = [ libgtop xmessage which ];
+
+  installPhase = ''
+    mkdir -p $out/bin/
+    cp das_watchdog $out/bin/
+    cp test_rt $out/bin/
+  '';
+
+  meta = with lib; {
+    homepage = "https://github.com/kmatheussen/das_watchdog";
+    description = "A general watchdog for the linux operating system";
+    longDescription = ''
+      It should run in the background at all times to ensure a realtime process
+      won't hang the machine.";
+    '';
+    license = licenses.free;
+    maintainers = [ maintainers.magnetophon ];
+    platforms = platforms.linux;
+  };
+}