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/build-support/fetchgx/default.nix

@@ -0,0 +1,30 @@
+{ stdenvNoCC, gx, gx-go, go, cacert }:
+
+{ name, src, sha256 }:
+
+stdenvNoCC.mkDerivation {
+  name = "${name}-gxdeps";
+  inherit src;
+
+  nativeBuildInputs = [ cacert go gx gx-go ];
+
+  outputHashAlgo = "sha256";
+  outputHashMode = "recursive";
+  outputHash = sha256;
+
+  dontConfigure = true;
+  doCheck = false;
+  doInstallCheck = false;
+
+  buildPhase = ''
+    export GOPATH=$(pwd)/vendor
+    mkdir -p vendor
+    gx install
+  '';
+
+  installPhase = ''
+    mv vendor $out
+  '';
+
+  preferLocalBuild = true;
+}