ref-manual/variables.rst: document WIC_CREATE_EXTRA_ARGS

Fixes [YOCTO #15509]

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
(From yocto-docs rev: f1cdecb6da91dbfac59359c83038cb4a4c36ad0a)

Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/variables.rst

@@ -10937,6 +10937,20 @@ system and gives an overview of their function and contents.
       Specifies the timeout in seconds used by the ``watchdog-config`` recipe
       and also by ``systemd`` during reboot. The default is 60 seconds.
 
+   :term:`WIC_CREATE_EXTRA_ARGS`
+      If the :term:`IMAGE_FSTYPES` variable contains "wic", the build
+      will generate a
+      :ref:`Wic image <dev-manual/wic:creating partitioned images using wic>`
+      automatically when BitBake builds an image recipe. As part of
+      this process BitBake will invoke the "`wic create`" command. The
+      :term:`WIC_CREATE_EXTRA_ARGS` variable is placed at the end of this
+      command which allows the user to supply additional arguments.
+
+      One such useful purpose for this mechanism is to add the ``-D`` (or
+      ``--debug``) argument to the "`wic create`" command. This increases the
+      amount of debugging information written out to the Wic log during the
+      Wic creation process.
+
    :term:`WIC_SECTOR_SIZE`
       The variable :term:`WIC_SECTOR_SIZE` controls the sector size of Wic
       images. In the background, this controls the value of the