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/security/signify/default.nix

@@ -0,0 +1,36 @@
+{ lib, stdenv, fetchFromGitHub, libbsd, pkg-config }:
+
+stdenv.mkDerivation rec {
+  pname = "signify";
+  version = "31";
+
+  src = fetchFromGitHub {
+    owner = "aperezdc";
+    repo = "signify";
+    rev = "v${version}";
+    sha256 = "sha256-y9jWG1JJhYCn6e5E2qjVqK8nmZpktiB7d9e9uP+3DLo=";
+  };
+
+  doCheck = true;
+
+  nativeBuildInputs = [ pkg-config ];
+  buildInputs = [ libbsd ];
+
+  postPatch = ''
+    substituteInPlace Makefile --replace "shell pkg-config" "shell $PKG_CONFIG"
+  '';
+
+  installFlags = [ "PREFIX=$(out)" ];
+
+  meta = with lib; {
+    description = "OpenBSD signing tool";
+    longDescription = ''
+      OpenBSDs signing tool, which uses the Ed25519 public key signature system
+      for fast signing and verification of messages using small public keys.
+    '';
+    homepage = "https://www.tedunangst.com/flak/post/signify";
+    license = licenses.isc;
+    maintainers = [ maintainers.rlupton20 ];
+    platforms = platforms.linux;
+  };
+}