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/development/beam-modules/fetch-hex.nix

@@ -0,0 +1,38 @@
+{ lib, stdenv, fetchurl }:
+
+{ pkg
+, version
+, sha256
+, meta ? { }
+}:
+
+with lib;
+
+stdenv.mkDerivation ({
+  pname = "hex-source-${pkg}";
+  inherit version;
+  dontBuild = true;
+  dontConfigure = true;
+  dontFixup = true;
+
+  src = fetchurl {
+    url = "https://repo.hex.pm/tarballs/${pkg}-${version}.tar";
+    inherit sha256;
+  };
+
+  unpackCmd = ''
+    tar -xf $curSrc contents.tar.gz
+    mkdir contents
+    tar -C contents -xzf contents.tar.gz
+  '';
+
+  installPhase = ''
+    runHook preInstall
+    mkdir "$out"
+    cp -Hrt "$out" .
+    success=1
+    runHook postInstall
+  '';
+
+  inherit meta;
+})