> Hi, I see you are using nrf.
>
> Signing, building, and hex merging of multiple images in a single west command is supported
> out-of-the box with the nRF Connect SDK, which uses a patched Zephyr.

> So if not using vanilla Zephyr is an option then see:
>
> https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/nrf9160/http_application_update/README.html#http-application-update-sample
> https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/ug_multi_image.html

I second Sebastian's suggestion to look at nRF Connect SDK (NCS).
It has useful features for building OTA binaries for nRF devices.

> -----
>
> West seems like the ideal tool to use for this, it boils down to a manifest repo (for project & dependencies checkout), and then a series of commands to build the various artifacts and merge & sign them. For example:
>
> west init -m git@...:SomeManifestRepo.git
> west build --board=theboard -d build-mcuboot -s mcuboot/boot/zephyr -- -DBOARD_ROOT=/abs/path/to/app
> west build --board=theboard -d build-app -s app -- -DBOARD_ROOT=/abs/path/to/app
> west sign ...
>
> However, it would be nice to be able to glue this all together with
> some script etc to simplify the extra elements of the west commands
> ('theboard' 'BOARD_ROOT') etc.

No matter what you choose to use (mainline or NCS), though, you can
always tell 'west build' your default board like this:

  west config build.board theboard

https://docs.zephyrproject.org/latest/guides/west/build-flash-debug.html#configuration-options

The build.board value will be used if you don't provide --board
(provided BOARD is also unset in the calling environment).

I thought about your BOARD_ROOT question. I've gotten other similar
requests recently, and I agree it would be useful, so I've proposed a
new "build.cmake-args" config option:

  https://github.com/zephyrproject-rtos/zephyr/pull/21251

With the patch from #21251, you can save your BOARD_ROOT like this:

  west config build.cmake-args -- -DBOARD_ROOT=/abs/path/to/app

Your one-time setup work would then be:

  west init -m git@.../SomeManifestRepo.git
  west update
  west config build.board theboard
  west config build.cmake-args -- -DBOARD_ROOT=/abs/path/to/app

Note that plain 'west config var val' sets configuration options locally
(just for your west installation). See the --global and --system options
in the 'west config' documentation for alternatives.

  # build and flash
  west build -d build-mcuboot -s mcuboot/boot/zephyr
  west build -d build-app -s app
  west sign ...

> And here is where I become unsure of how this glue script/(c)makefile/etc fits into the topology of the project.. The natural place for the script to run from is the west installation folder itself (ie, the parent folder of all the subprojects) however the natural place for it to 'live' is in the 'manifest-repo'.
>
> Alternatives:
>  - copy 'glue' script into west installation folder ?
>  - west commands ? in the manifest repo, or maybe another common lib etc.

I hope the above is what you're looking for.

Note 'west build' can only compile one Zephyr application at a time.
The NCS can build application and mcuboot binaries at once out of the
box, for reference.

Please test and comment in the PR if you get a chance.