ref-manual: correctly document the difference between auto.conf and newly added toolcfg.conf

[AG: Add reference to YP Autobuilder]

(From yocto-docs rev: f23b93594dbe7e5df9ec55371e4aab4b7b8c50b9)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

documentation/ref-manual/fragments.rst

@@ -94,7 +94,7 @@ Note that in this case, the fragment will be defined twice in
 :term:`OE_FRAGMENTS`, and the last value is taken into account:
 
 .. code-block::
-   :caption: build/conf/auto.conf
+   :caption: build/conf/toolcfg.conf
 
    OE_FRAGMENTS += " ... machine/qemuarm64 machine/qemux86-64"
 
@@ -103,7 +103,7 @@ In the above example, the value of :term:`MACHINE` is thus equal to
 
 When a fragment is enabled with :ref:`ref-bitbake-config-build-enable-fragment`,
 its name is automatically appended to the :term:`OE_FRAGMENTS` variable in
-:ref:`structure-build-conf-auto.conf`.
+:ref:`structure-build-conf-toolcfg.conf`.
 
 .. note::
 

documentation/ref-manual/structure.rst

@@ -356,15 +356,24 @@ This configuration file is generated by :doc:`bblock </dev-manual/bblock>` and
 contains the signatures locked by ``bblock``. By default, it does not exist
 and will be created upon the first invocation of ``bblock``.
 
-.. _structure-build-conf-auto.conf:
+.. _structure-build-conf-toolcfg.conf:
 
-``build/conf/auto.conf``
-------------------------
+``build/conf/toolcfg.conf``
+---------------------------
 
 This file contains configuration variables that are automatically modified by
 tools such as :oe_git:`bitbake-config-build </bitbake/tree/bin/bitbake-config-build>`.
 This file should not be modified manually.
 
+.. _structure-build-conf-auto.conf:
+
+``build/conf/auto.conf``
+------------------------
+
+This file is intended for use by continuous integration environments, such as the
+Yocto Project's :doc:`Autobuilder </test-manual/understand-autobuilder>`. It
+should not be created or modified when running local builds.
+
 .. _structure-build-downloads:
 
 ``build/downloads/``