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/testing/test-instrumentation.nix

@@ -0,0 +1,137 @@
+# This module allows the test driver to connect to the virtual machine
+# via a root shell attached to port 514.
+
+{ options, config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  qemu-common = import ../../lib/qemu-common.nix { inherit lib pkgs; };
+in
+
+{
+
+  config = {
+
+    systemd.services.backdoor =
+      { wantedBy = [ "multi-user.target" ];
+        requires = [ "dev-hvc0.device" "dev-${qemu-common.qemuSerialDevice}.device" ];
+        after = [ "dev-hvc0.device" "dev-${qemu-common.qemuSerialDevice}.device" ];
+        script =
+          ''
+            export USER=root
+            export HOME=/root
+            export DISPLAY=:0.0
+
+            source /etc/profile
+
+            # Don't use a pager when executing backdoor
+            # actions. Because we use a tty, commands like systemctl
+            # or nix-store get confused into thinking they're running
+            # interactively.
+            export PAGER=
+
+            cd /tmp
+            exec < /dev/hvc0 > /dev/hvc0
+            while ! exec 2> /dev/${qemu-common.qemuSerialDevice}; do sleep 0.1; done
+            echo "connecting to host..." >&2
+            stty -F /dev/hvc0 raw -echo # prevent nl -> cr/nl conversion
+            echo
+            PS1= exec /bin/sh
+          '';
+        serviceConfig.KillSignal = "SIGHUP";
+      };
+
+    # Prevent agetty from being instantiated on the serial device, since it
+    # interferes with the backdoor (writes to it will randomly fail
+    # with EIO).  Likewise for hvc0.
+    systemd.services."serial-getty@${qemu-common.qemuSerialDevice}".enable = false;
+    systemd.services."serial-getty@hvc0".enable = false;
+
+    # Only set these settings when the options exist. Some tests (e.g. those
+    # that do not specify any nodes, or an empty attr set as nodes) will not
+    # have the QEMU module loaded and thuse these options can't and should not
+    # be set.
+    virtualisation = lib.optionalAttrs (options ? virtualisation.qemu) {
+      qemu = {
+        # Only use a serial console, no TTY.
+        # NOTE: optionalAttrs
+        #       test-instrumentation.nix appears to be used without qemu-vm.nix, so
+        #       we avoid defining consoles if not possible.
+        # TODO: refactor such that test-instrumentation can import qemu-vm
+        #       or declare virtualisation.qemu.console option in a module that's always imported
+        consoles = [ qemu-common.qemuSerialDevice ];
+        package  = lib.mkDefault pkgs.qemu_test;
+      };
+    };
+
+    boot.kernel.sysctl = {
+      "kernel.hung_task_timeout_secs" = 600;
+      # Panic on out-of-memory conditions rather than letting the
+      # OOM killer randomly get rid of processes, since this leads
+      # to failures that are hard to diagnose.
+      "vm.panic_on_oom" = lib.mkDefault 2;
+    };
+
+    boot.kernelParams = [
+      "console=${qemu-common.qemuSerialDevice}"
+      # Panic if an error occurs in stage 1 (rather than waiting for
+      # user intervention).
+      "panic=1" "boot.panic_on_fail"
+      # Using acpi_pm as a clock source causes the guest clock to
+      # slow down under high host load.  This is usually a bad
+      # thing, but for VM tests it should provide a bit more
+      # determinism (e.g. if the VM runs at lower speed, then
+      # timeouts in the VM should also be delayed).
+      "clock=acpi_pm"
+    ];
+
+    # `xwininfo' is used by the test driver to query open windows.
+    environment.systemPackages = [ pkgs.xorg.xwininfo ];
+
+    # Log everything to the serial console.
+    services.journald.extraConfig =
+      ''
+        ForwardToConsole=yes
+        MaxLevelConsole=debug
+      '';
+
+    systemd.extraConfig = ''
+      # Don't clobber the console with duplicate systemd messages.
+      ShowStatus=no
+      # Allow very slow start
+      DefaultTimeoutStartSec=300
+    '';
+    systemd.user.extraConfig = ''
+      # Allow very slow start
+      DefaultTimeoutStartSec=300
+    '';
+
+    boot.consoleLogLevel = 7;
+
+    # Prevent tests from accessing the Internet.
+    networking.defaultGateway = mkOverride 150 "";
+    networking.nameservers = mkOverride 150 [ ];
+
+    system.requiredKernelConfig = with config.lib.kernelConfig; [
+      (isYes "SERIAL_8250_CONSOLE")
+      (isYes "SERIAL_8250")
+      (isEnabled "VIRTIO_CONSOLE")
+    ];
+
+    networking.usePredictableInterfaceNames = false;
+
+    # Make it easy to log in as root when running the test interactively.
+    users.users.root.initialHashedPassword = mkOverride 150 "";
+
+    services.xserver.displayManager.job.logToJournal = true;
+
+    # Make sure we use the Guest Agent from the QEMU package for testing
+    # to reduce the closure size required for the tests.
+    services.qemuGuest.package = pkgs.qemu_test.ga;
+
+    # Squelch warning about unset system.stateVersion
+    system.stateVersion = lib.mkDefault lib.trivial.release;
+  };
+
+}