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/stdenv/custom/default.nix

@@ -0,0 +1,25 @@
+{ lib
+, localSystem, crossSystem, config, overlays, crossOverlays ? []
+}:
+
+assert crossSystem == localSystem;
+
+let
+  bootStages = import ../. {
+    inherit lib localSystem crossSystem overlays;
+    # Remove config.replaceStdenv to ensure termination.
+    config = builtins.removeAttrs config [ "replaceStdenv" ];
+  };
+
+in bootStages ++ [
+
+  # Additional stage, built using custom stdenv
+  (vanillaPackages: {
+    inherit config overlays;
+    stdenv =
+      assert vanillaPackages.hostPlatform == localSystem;
+      assert vanillaPackages.targetPlatform == localSystem;
+      config.replaceStdenv { pkgs = vanillaPackages; };
+  })
+
+]