make kernel builder callPackage'able

kernel/default.nix

@@ -0,0 +1,43 @@
+{
+  callPackage
+, buildPackages
+, stdenvNoCC
+, fetchFromGitHub
+
+, config
+}:
+let
+  source = fetchFromGitHub {
+    owner = "torvalds";
+    repo = "linux";
+    rev = "3d7cb6b04c3f3115719235cc6866b10326de34cd";  # v5.19
+    hash = "sha256-OVsIRScAnrPleW1vbczRAj5L/SGGht2+GnvZJClMUu4=";
+  };
+
+  # The kernel is huge and takes a long time just to
+  # download and unpack. This derivation creates
+  # a source tree in a suitable shape to build from -
+  # today it just patches some scripts but as we add
+  # support for boards/SoCs we expect the scope of
+  # "pre-treatment" to grow
+
+  tree = stdenvNoCC.mkDerivation {
+    name = "spindled-kernel-tree";
+    src = source;
+    phases = [ "unpackPhase" "patchScripts" "installPhase" ];
+    patchScripts = ''
+      patchShebangs scripts/
+      # substituteInPlace Makefile --replace /bin/pwd ${buildPackages.pkgs.coreutils}/bin/pwd
+    '';
+    installPhase = ''
+      mkdir -p $out
+      cp -a . $out
+    '';
+  };
+in
+{
+  vmlinux = callPackage ./vmlinux.nix {
+    inherit tree;
+    inherit config;
+  };
+}