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/filesystems/mtools/UNUSED-darwin.patch

@@ -0,0 +1,11 @@
+--- mtools/sysincludes.h.orig	2017-04-01 20:59:46.083196540 +0100
++++ mtools/sysincludes.h	2017-04-01 20:59:12.855030456 +0100
+@@ -103,7 +103,7 @@
+ # define PACKED __attribute__ ((packed))
+ # if __GNUC__ == 2 && __GNUC_MINOR__ > 6 || __GNUC__ >= 3
+ /* gcc 2.6.3 doesn't have "unused" */		/* mool */
+-#  define UNUSED(x) x __attribute__ ((unused));x
++#  define UNUSED(x) x
+ #  define UNUSEDP __attribute__ ((unused))
+ # else
+ #  define UNUSED(x) x

pkgs/tools/filesystems/mtools/default.nix

@@ -0,0 +1,27 @@
+{ lib, stdenv, fetchurl, libiconv }:
+
+stdenv.mkDerivation rec {
+  pname = "mtools";
+  version = "4.0.38";
+
+  src = fetchurl {
+    url = "mirror://gnu/mtools/${pname}-${version}.tar.bz2";
+    sha256 = "sha256-e5RIX0huffCMymiwChZKE8049MY8uGhNGIdZ7nvF5yk=";
+  };
+
+  patches = lib.optional stdenv.isDarwin ./UNUSED-darwin.patch;
+
+  # fails to find X on darwin
+  configureFlags = lib.optional stdenv.isDarwin "--without-x";
+
+  buildInputs = lib.optional stdenv.isDarwin libiconv;
+
+  doCheck = true;
+
+  meta = with lib; {
+    homepage = "https://www.gnu.org/software/mtools/";
+    description = "Utilities to access MS-DOS disks";
+    platforms = platforms.unix;
+    license = licenses.gpl3;
+  };
+}