doc: develop: toolchains: Remove 'xtools' documentation

The `xtools` toolchain variant has been deprecated since Zephyr v3.3.0 and
now removed.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

doc/develop/test/twister.rst

@@ -116,7 +116,6 @@ required for best test coverage for this specific board:
   toolchain:
     - zephyr
     - gnuarmemb
-    - xtools
   supported:
     - arduino_gpio
     - arduino_i2c

doc/develop/toolchains/crosstool_ng.rst

@@ -1,49 +0,0 @@
-.. _toolchain_xtools:
-
-Crosstool-NG (Deprecated)
-#########################
-
-.. warning::
-
-   ``xtools`` toolchain variant is deprecated. The
-   :ref:`cross-compile toolchain variant <other_x_compilers>` should be used
-   when using a custom toolchain built with Crosstool-NG.
-
-You can build toolchains from source code using crosstool-NG.
-
-#. Follow the steps on the crosstool-NG website to `prepare your host
-   <http://crosstool-ng.github.io/docs/os-setup/>`_.
-
-#. Follow the `Zephyr SDK with Crosstool NG instructions
-   <https://github.com/zephyrproject-rtos/sdk-ng/blob/master/README.md>`_ to
-   build your toolchain. Repeat as necessary to build toolchains for multiple
-   target architectures.
-
-   You will need to clone the ``sdk-ng`` repo and run the following command:
-
-   .. code-block:: console
-
-      ./go.sh <arch>
-
-   .. note::
-
-      Currently, only i586 and Arm toolchain builds are verified.
-
-#. :ref:`Set these environment variables <env_vars>`:
-
-   - Set :envvar:`ZEPHYR_TOOLCHAIN_VARIANT` to ``xtools``.
-   - Set :envvar:`XTOOLS_TOOLCHAIN_PATH` to the toolchain build directory.
-
-#. To check that you have set these variables correctly in your current
-   environment, follow these example shell sessions (the
-   :envvar:`XTOOLS_TOOLCHAIN_PATH` values may be different on your system):
-
-   .. code-block:: console
-
-      # Linux, macOS:
-      $ echo $ZEPHYR_TOOLCHAIN_VARIANT
-      xtools
-      $ echo $XTOOLS_TOOLCHAIN_PATH
-      /Volumes/CrossToolNGNew/build/output/
-
-.. _crosstool-ng site: http://crosstool-ng.org

doc/develop/toolchains/index.rst

@@ -16,7 +16,6 @@ Guides on how to set up toolchains for Zephyr development.
    gnu_arm_embedded.rst
    intel_oneapi_toolkit.rst
 
-   crosstool_ng.rst
    host.rst
    other_x_compilers.rst
    custom_cmake.rst

doc/releases/release-notes-3.3.rst

@@ -186,7 +186,7 @@ Removed APIs in this release
 Deprecated in this release
 ==========================
 
-* :ref:`xtools toolchain variant <toolchain_xtools>` is now deprecated. When using a
+* ``xtools`` toolchain variant is now deprecated. When using a
   custom toolchain built with Crosstool-NG, the
   :ref:`cross-compile toolchain variant <other_x_compilers>` should be used instead.