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>

nixos/doc/manual/development/testing-installer.chapter.md

@@ -0,0 +1,18 @@
+# Testing the Installer {#ch-testing-installer}
+
+Building, burning, and booting from an installation CD is rather
+tedious, so here is a quick way to see if the installer works properly:
+
+```ShellSession
+# mount -t tmpfs none /mnt
+# nixos-generate-config --root /mnt
+$ nix-build '<nixpkgs/nixos>' -A config.system.build.nixos-install
+# ./result/bin/nixos-install
+```
+
+To start a login shell in the new NixOS installation in `/mnt`:
+
+```ShellSession
+$ nix-build '<nixpkgs/nixos>' -A config.system.build.nixos-enter
+# ./result/bin/nixos-enter
+```