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/installer/kexec/kexec-boot.nix

@@ -0,0 +1,51 @@
+# This module exposes a config.system.build.kexecBoot attribute,
+# which returns a directory with kernel, initrd and a shell script
+# running the necessary kexec commands.
+
+# It's meant to be scp'ed to a machine with working ssh and kexec binary
+# installed.
+
+# This is useful for (cloud) providers where you can't boot a custom image, but
+# get some Debian or Ubuntu installation.
+
+{ pkgs
+, modulesPath
+, config
+, ...
+}:
+{
+  imports = [
+    (modulesPath + "/installer/netboot/netboot-minimal.nix")
+  ];
+
+  config = {
+    system.build.kexecBoot =
+      let
+        kexecScript = pkgs.writeScript "kexec-boot" ''
+          #!/usr/bin/env bash
+          if ! kexec -v >/dev/null 2>&1; then
+            echo "kexec not found: please install kexec-tools" 2>&1
+            exit 1
+          fi
+          SCRIPT_DIR=$( cd -- "$( dirname -- "''${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+          kexec --load ''${SCRIPT_DIR}/bzImage \
+            --initrd=''${SCRIPT_DIR}/initrd.gz \
+            --command-line "init=${config.system.build.toplevel}/init ${toString config.boot.kernelParams}"
+          kexec -e
+        ''; in
+      pkgs.linkFarm "kexec-tree" [
+        {
+          name = "initrd.gz";
+          path = "${config.system.build.netbootRamdisk}/initrd";
+        }
+        {
+          name = "bzImage";
+          path = "${config.system.build.kernel}/${config.system.boot.loader.kernelFile}";
+        }
+        {
+          name = "kexec-boot";
+          path = kexecScript;
+        }
+      ];
+  };
+}