doc: improve docs on building without west

maintain those additional repositories, adding new ones as necessary

and keeping existing ones up to date at the latest revisions.

Specifying Modules

------------------

Building applications

---------------------

You can build a Zephyr application using CMake and Ninja (or make) directly

without west installed if you specify any modules manually.

.. zephyr-app-commands::

   :zephyr-app: samples/hello_world

   :tool: cmake

   :goals: build

   :gen-args: -DZEPHYR_MODULES=module1;module2;...

   :compact:

If you have west installed, the Zephyr build system will use it to set

:ref:`ZEPHYR_MODULES <important-build-vars>`. If you don't have west

installed and your application does not need any of these

repositories, the build will still work.

When building with west installed, the Zephyr build system will use it to set

:ref:`ZEPHYR_MODULES <important-build-vars>`.

If you don't have west installed and your application does not need any of

these repositories, the build will still work.

If you don't have west installed and your application *does* need one

of these repositories, you must set :makevar:`ZEPHYR_MODULES`

yourself. See :ref:`modules` for details.

yourself as shown above.

See :ref:`modules` for more details.

Flashing and Debugging

----------------------