Generate pinetime-recovery : a light version of InfiniTime design to be used as a recovery firmware : it only provides basic UI and BLE connectivity for OTA.

This new FW is build on the same codebasse than the actual InfiniTime. Only the display task is different (this allows to remove lvgl from the recovery fw, which is very heavy).

CMake builds and docker have been modified accordingly.
Note than the fw is converted into an image and then into a DFU in the cmake build (previously, it was only done in the

tools/mcuboot/imgtool.nix

@@ -0,0 +1,30 @@
+#
+# Nix environment for imgtool
+#
+# To install the environment
+#
+# $ nix-env --file imgtool.nix --install env-imgtool
+#
+# To load the environment
+#
+# $ load-env-imgtool
+#
+with import <nixpkgs> {};
+let
+  # Nixpkgs has fairly recent versions of the dependencies, so we can
+  # rely on them without having to build our own derivations.
+  imgtoolPythonEnv = python37.withPackages (
+    _: [
+      python37.pkgs.click
+      python37.pkgs.cryptography
+      python37.pkgs.intelhex
+      python37.pkgs.setuptools
+      python37.pkgs.cbor
+    ]
+  );
+in
+myEnvFun {
+  name = "imgtool";
+
+  buildInputs = [ imgtoolPythonEnv ];
+}