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/plugins.nix

@@ -0,0 +1,29 @@
+{ lib }:
+# helper functions for packaging programs with plugin systems
+{
+
+  /* Takes a list of expected plugin names
+   * and compares it to the found plugins given in the file,
+   * one plugin per line.
+   * If the lists differ, the build fails with a nice message.
+   *
+   * This is helpful to ensure maintainers don’t miss
+   * the addition or removal of a plugin.
+   */
+  diffPlugins = expectedPlugins: foundPluginsFilePath: ''
+     # sort both lists first
+     plugins_expected=$(mktemp)
+     (${lib.concatMapStrings (s: "echo \"${s}\";") expectedPlugins}) \
+       | sort -u > "$plugins_expected"
+     plugins_found=$(mktemp)
+     sort -u "${foundPluginsFilePath}" > "$plugins_found"
+
+     if ! mismatches="$(diff -y "$plugins_expected" "$plugins_found")"; then
+       echo "The the list of expected plugins (left side) doesn't match" \
+           "the list of plugins we found (right side):" >&2
+       echo "$mismatches" >&2
+       exit 1
+     fi
+   '';
+
+}