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>

pkgs/tools/filesystems/btrfs-heatmap/default.nix

@@ -0,0 +1,42 @@
+{ stdenv, lib
+, fetchFromGitHub
+, python3
+, installShellFiles
+}:
+
+stdenv.mkDerivation rec {
+  pname = "btrfs-heatmap";
+  version = "9";
+
+  src = fetchFromGitHub {
+    owner = "knorrie";
+    repo = "btrfs-heatmap";
+    rev = "v${version}";
+    sha256 = "sha256-yCkuZqWwxrs2eS7EXY6pAOVVVSq7dAMxJtf581gX8vg=";
+  };
+
+  buildInputs = [ python3 ];
+  nativeBuildInputs = [ python3.pkgs.wrapPython installShellFiles ];
+
+  outputs = [ "out" "man" ];
+
+  installPhase = ''
+    runHook preInstall
+
+    install -Dm 0755 btrfs-heatmap $out/sbin/btrfs-heatmap
+    installManPage man/btrfs-heatmap.1
+
+    buildPythonPath ${python3.pkgs.btrfs}
+    patchPythonScript $out/sbin/btrfs-heatmap
+
+    runHook postInstall
+  '';
+
+  meta = with lib; {
+    description = "Visualize the layout of a mounted btrfs";
+    homepage = "https://github.com/knorrie/btrfs-heatmap";
+    license = licenses.mit;
+    platforms = platforms.linux;
+    maintainers = [ maintainers.evils ];
+  };
+}