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/services/misc/nix-gc.nix

@@ -0,0 +1,106 @@
+{ config, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.nix.gc;
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    nix.gc = {
+
+      automatic = mkOption {
+        default = false;
+        type = types.bool;
+        description = "Automatically run the garbage collector at a specific time.";
+      };
+
+      dates = mkOption {
+        type = types.str;
+        default = "03:15";
+        example = "weekly";
+        description = ''
+          How often or when garbage collection is performed. For most desktop and server systems
+          a sufficient garbage collection is once a week.
+
+          The format is described in
+          <citerefentry><refentrytitle>systemd.time</refentrytitle>
+          <manvolnum>7</manvolnum></citerefentry>.
+        '';
+      };
+
+      randomizedDelaySec = mkOption {
+        default = "0";
+        type = types.str;
+        example = "45min";
+        description = ''
+          Add a randomized delay before each garbage collection.
+          The delay will be chosen between zero and this value.
+          This value must be a time span in the format specified by
+          <citerefentry><refentrytitle>systemd.time</refentrytitle>
+          <manvolnum>7</manvolnum></citerefentry>
+        '';
+      };
+
+      persistent = mkOption {
+        default = true;
+        type = types.bool;
+        example = false;
+        description = ''
+          Takes a boolean argument. If true, the time when the service
+          unit was last triggered is stored on disk. When the timer is
+          activated, the service unit is triggered immediately if it
+          would have been triggered at least once during the time when
+          the timer was inactive. Such triggering is nonetheless
+          subject to the delay imposed by RandomizedDelaySec=. This is
+          useful to catch up on missed runs of the service when the
+          system was powered down.
+        '';
+      };
+
+      options = mkOption {
+        default = "";
+        example = "--max-freed $((64 * 1024**3))";
+        type = types.str;
+        description = ''
+          Options given to <filename>nix-collect-garbage</filename> when the
+          garbage collector is run automatically.
+        '';
+      };
+
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = {
+    assertions = [
+      {
+        assertion = cfg.automatic -> config.nix.enable;
+        message = ''nix.gc.automatic requires nix.enable'';
+      }
+    ];
+
+    systemd.services.nix-gc = lib.mkIf config.nix.enable {
+      description = "Nix Garbage Collector";
+      script = "exec ${config.nix.package.out}/bin/nix-collect-garbage ${cfg.options}";
+      startAt = optional cfg.automatic cfg.dates;
+    };
+
+    systemd.timers.nix-gc = lib.mkIf cfg.automatic {
+      timerConfig = {
+        RandomizedDelaySec = cfg.randomizedDelaySec;
+        Persistent = cfg.persistent;
+      };
+    };
+
+  };
+
+}