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/applications/graphics/potrace/default.nix

@@ -0,0 +1,26 @@
+{ lib, stdenv, fetchurl, zlib }:
+
+stdenv.mkDerivation rec {
+  pname = "potrace";
+  version = "1.16";
+
+  src = fetchurl {
+    url = "http://potrace.sourceforge.net/download/${version}/potrace-${version}.tar.gz";
+    sha256 = "1k3sxgjqq0jnpk9xxys05q32sl5hbf1lbk1gmfxcrmpdgnhli0my";
+  };
+
+  configureFlags = [ "--with-libpotrace" ];
+
+  buildInputs = [ zlib ];
+
+  enableParallelBuilding = true;
+  doCheck = true;
+
+  meta = with lib; {
+    homepage = "http://potrace.sourceforge.net/";
+    description = "A tool for tracing a bitmap, which means, transforming a bitmap into a smooth, scalable image";
+    platforms = platforms.unix;
+    maintainers = [ maintainers.pSub ];
+    license = licenses.gpl2;
+  };
+}