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>

lib/tests/check-eval.nix

@@ -0,0 +1,7 @@
+# Throws an error if any of our lib tests fail.
+
+let tests = [ "misc" "systems" ];
+    all = builtins.concatLists (map (f: import (./. + "/${f}.nix")) tests);
+in if all == []
+     then null
+   else throw (builtins.toJSON all)