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/dhall/directory-to-nix.nix

@@ -0,0 +1,25 @@
+{ dhallPackages, dhallPackageToNix}:
+
+# `dhallDirectoryToNix is a utility function to take a directory of Dhall files
+# and read them in as a Nix expression.
+#
+# This function is similar to `dhallToNix`, but takes a Nixpkgs Dhall package
+# as input instead of raw Dhall code.
+#
+# Note that this uses "import from derivation" (IFD), meaning that Nix will
+# perform a build during the evaluation phase if you use this
+# `dhallDirectoryToNix` utility.  It is not possible to use
+# `dhallDirectoryToNix` in Nixpkgs, since the Nixpkgs Hydra doesn't allow IFD.
+
+{ src
+, # The file to import, relative to the src root directory
+  file ? "package.dhall"
+}@args:
+
+let
+  generatedPkg = dhallPackages.generateDhallDirectoryPackage args;
+
+  builtPkg = dhallPackages.callPackage generatedPkg { };
+
+in
+  dhallPackageToNix builtPkg