ref-manual: add virtual-slash QA check

Add the new virtual-slash QA check to the insane class section and the
QA checks section.

(From yocto-docs rev: fdca0217558185eca67f7ec04b9d282b7819d107)

Signed-off-by: Paul Eggleton <paul.eggleton@microsoft.com>
Reviewed-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/classes.rst

@@ -1582,6 +1582,12 @@ The tests you can list with the :term:`WARN_QA` and
       This is only relevant when you are using runtime package management
       on your target system.
 
+-  ``virtual-slash:`` Checks to see if ``virtual/`` is being used in
+   :term:`RDEPENDS` or :term:`RPROVIDES`, which is not good practice ---
+   ``virtual/`` is a convention intended for use in the build context
+   (i.e. :term:`PROVIDES` and :term:`DEPENDS`) rather than the runtime
+   context.
+
 -  ``xorg-driver-abi:`` Checks that all packages containing Xorg
    drivers have ABI dependencies. The ``xserver-xorg`` recipe provides
    driver ABI names. All drivers should depend on the ABI versions that

documentation/ref-manual/qa-checks.rst

@@ -799,6 +799,14 @@ Errors and Warnings
     section in the Yocto Project Development Tasks Manual. See also the
     ":ref:`ref-classes-ptest`" section.
 
+.. _qa-check-virtual-slash:
+
+- ``<variable> is set to <value> but the substring 'virtual/' holds no meaning in this context. It only works for build time dependencies, not runtime ones. It is suggested to use 'VIRTUAL-RUNTIME_' variables instead.``
+
+    ``virtual/`` is a convention intended for use in the build context
+    (i.e. :term:`PROVIDES` and :term:`DEPENDS`) rather than the runtime
+    context (i.e. :term:`RPROVIDES` and :term:`RDEPENDS`). Use
+    :term:`VIRTUAL-RUNTIME` variables instead for the latter.
 
 
 Configuring and Disabling QA Checks