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/tests/btrbk.nix

@@ -0,0 +1,110 @@
+import ./make-test-python.nix ({ pkgs, ... }:
+
+  let
+    privateKey = ''
+      -----BEGIN OPENSSH PRIVATE KEY-----
+      b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAMwAAAAtzc2gtZW
+      QyNTUxOQAAACBx8UB04Q6Q/fwDFjakHq904PYFzG9pU2TJ9KXpaPMcrwAAAJB+cF5HfnBe
+      RwAAAAtzc2gtZWQyNTUxOQAAACBx8UB04Q6Q/fwDFjakHq904PYFzG9pU2TJ9KXpaPMcrw
+      AAAEBN75NsJZSpt63faCuaD75Unko0JjlSDxMhYHAPJk2/xXHxQHThDpD9/AMWNqQer3Tg
+      9gXMb2lTZMn0pelo8xyvAAAADXJzY2h1ZXR6QGt1cnQ=
+      -----END OPENSSH PRIVATE KEY-----
+    '';
+    publicKey = ''
+      ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHHxQHThDpD9/AMWNqQer3Tg9gXMb2lTZMn0pelo8xyv
+    '';
+  in
+  {
+    name = "btrbk";
+    meta = with pkgs.lib; {
+      maintainers = with maintainers; [ symphorien ];
+    };
+
+    nodes = {
+      archive = { ... }: {
+        environment.systemPackages = with pkgs; [ btrfs-progs ];
+        # note: this makes the privateKey world readable.
+        # don't do it with real ssh keys.
+        environment.etc."btrbk_key".text = privateKey;
+        services.btrbk = {
+          extraPackages = [ pkgs.lz4 ];
+          instances = {
+            remote = {
+              onCalendar = "minutely";
+              settings = {
+                ssh_identity = "/etc/btrbk_key";
+                ssh_user = "btrbk";
+                stream_compress = "lz4";
+                volume = {
+                  "ssh://main/mnt" = {
+                    target = "/mnt";
+                    snapshot_dir = "btrbk/remote";
+                    subvolume = "to_backup";
+                  };
+                };
+              };
+            };
+          };
+        };
+      };
+
+      main = { ... }: {
+        environment.systemPackages = with pkgs; [ btrfs-progs ];
+        services.openssh = {
+          enable = true;
+          passwordAuthentication = false;
+          kbdInteractiveAuthentication = false;
+        };
+        services.btrbk = {
+          extraPackages = [ pkgs.lz4 ];
+          sshAccess = [
+            {
+              key = publicKey;
+              roles = [ "source" "send" "info" "delete" ];
+            }
+          ];
+          instances = {
+            local = {
+              onCalendar = "minutely";
+              settings = {
+                volume = {
+                  "/mnt" = {
+                    snapshot_dir = "btrbk/local";
+                    subvolume = "to_backup";
+                  };
+                };
+              };
+            };
+          };
+        };
+      };
+    };
+
+    testScript = ''
+      start_all()
+
+      # create btrfs partition at /mnt
+      for machine in (archive, main):
+        machine.succeed("dd if=/dev/zero of=/data_fs bs=120M count=1")
+        machine.succeed("mkfs.btrfs /data_fs")
+        machine.succeed("mkdir /mnt")
+        machine.succeed("mount /data_fs /mnt")
+
+      # what to backup and where
+      main.succeed("btrfs subvolume create /mnt/to_backup")
+      main.succeed("mkdir -p /mnt/btrbk/{local,remote}")
+
+      # check that local snapshots work
+      with subtest("local"):
+          main.succeed("echo foo > /mnt/to_backup/bar")
+          main.wait_until_succeeds("cat /mnt/btrbk/local/*/bar | grep foo")
+          main.succeed("echo bar > /mnt/to_backup/bar")
+          main.succeed("cat /mnt/btrbk/local/*/bar | grep foo")
+
+      # check that btrfs send/receive works and ssh access works
+      with subtest("remote"):
+          archive.wait_until_succeeds("cat /mnt/*/bar | grep bar")
+          main.succeed("echo baz > /mnt/to_backup/bar")
+          archive.succeed("cat /mnt/*/bar | grep bar")
+    '';
+  })