ref-manual: document RM_WORK_EXCLUDE_ITEMS variable

Add an explanation of the RM_WORK_EXCLUDE_ITEMS variable to both the
Reference Manual variables and classes sections.

(From yocto-docs rev: fa007992c5df04e51de4fbd8edbcf29583cb49f0)

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
(cherry picked from commit 62c96090be7aeffe7010b70e8dfd5166e506140f)
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Paul Barker <paul@pbarker.dev>

documentation/ref-manual/classes.rst

@@ -2856,6 +2856,13 @@ which can also be set in your ``local.conf`` file. Here is an example::
 
    RM_WORK_EXCLUDE += "busybox glibc"
 
+Finally, if you are using this class for a recipe but want to prevent
+:term:`BitBake` from deleting specific folders or files in that recipe's
+:term:`WORKDIR` (other than ``temp``), you can preserve those folders or
+files with the :term:`RM_WORK_EXCLUDE_ITEMS` variable as follows::
+
+   RM_WORK_EXCLUDE_ITEMS += "items_to_keep"
+
 .. _ref-classes-rootfs*:
 
 ``rootfs*``

documentation/ref-manual/variables.rst

@@ -7533,6 +7533,12 @@ system and gives an overview of their function and contents.
       specifies a list of recipes whose work directories should not be removed.
       See the ":ref:`ref-classes-rm-work`" section for more details.
 
+   :term:`RM_WORK_EXCLUDE_ITEMS`
+      With :ref:`ref-classes-rm-work` enabled, this variable specifies
+      a list of files or folders --- relative to the recipe's :term:`WORKDIR` ---
+      to be preserved.
+      See the ":ref:`ref-classes-rm-work`" section for more details.
+
    :term:`ROOT_HOME`
       Defines the root home directory. By default, this directory is set as
       follows in the BitBake configuration file::