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/modules/config/debug-info.nix

@@ -0,0 +1,45 @@
+{ config, lib, ... }:
+
+with lib;
+
+{
+
+  options = {
+
+    environment.enableDebugInfo = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Some NixOS packages provide debug symbols. However, these are
+        not included in the system closure by default to save disk
+        space. Enabling this option causes the debug symbols to appear
+        in <filename>/run/current-system/sw/lib/debug/.build-id</filename>,
+        where tools such as <command>gdb</command> can find them.
+        If you need debug symbols for a package that doesn't
+        provide them by default, you can enable them as follows:
+        <programlisting>
+        nixpkgs.config.packageOverrides = pkgs: {
+          hello = pkgs.hello.overrideAttrs (oldAttrs: {
+            separateDebugInfo = true;
+          });
+        };
+        </programlisting>
+      '';
+    };
+
+  };
+
+
+  config = mkIf config.environment.enableDebugInfo {
+
+    # FIXME: currently disabled because /lib is already in
+    # environment.pathsToLink, and we can't have both.
+    #environment.pathsToLink = [ "/lib/debug/.build-id" ];
+
+    environment.extraOutputsToInstall = [ "debug" ];
+
+    environment.variables.NIX_DEBUG_INFO_DIRS = [ "/run/current-system/sw/lib/debug" ];
+
+  };
+
+}