[marc-hb]

Add missing git submodule update as reported by @plbossart (thx!)

Also make the documentation ready for xtensa-build-zephyr.py
which... does not have any hack to automatically download git submodules
like the older .sh script has.

As a side-effect, this breaks down the process and adds an intermediate
west build step which removes one layer of indirection in case of some
Zephyr environment issue.

Cannot fully switch to the Python version yet because of bugs like
thesofproject/sof#5906 but do recommend users to
start trying it.

[marc-hb]

The many breathe warnings are unrelated to this. They're caused by the recent addition of __sparse_* attributes in the source code.
https://github.com/thesofproject/sof-docs/runs/6803642273?check_suite_focus=true
cc: @lyakh

EDIT: _sparse_cache warnings fixed in

• conf.py: cpp_id_attributes = ["__sparse_cache"] #414

/home/runner/work/sof-docs/sof-docs/api/audio-stream-api.rst:8: WARNING: Error when parsing function declaration.
If the function has no return type:
  Error in declarator or parameters and qualifiers
  Invalid definition: Expected identifier in nested name, got keyword: int [error at 10]
    static int audio_stream_set_params(struct  audio_stream   __sparse_cache  * buffer, struct  sof_ipc_stream_params  * params)
    ----------^
If the function has a return type:
  Error in declarator or parameters and qualifiers
  If pointer to member declarator:
    Invalid definition: Expected '::' in pointer to member (function). [error at 34]
      static int audio_stream_set_params(struct  audio_stream   __sparse_cache  * buffer, struct  sof_ipc_stream_params  * params)
      ----------------------------------^
  If declarator-id:
    Invalid definition: Expecting "," or ")" in parameters_and_qualifiers, got "*". [error at 74]
      static int audio_stream_set_params(struct  audio_stream   __sparse_cache  * buffer, struct  sof_ipc_stream_params  * params)
      --------------------------------------------------------------------------^

[marc-hb]

As usual to see a rendered version of the modified file go to "Files changed" -> "..." -> "View File"

[plbossart]

thanks @marc-hb