nixos: Add release note about vmVariant

nixos/doc/manual/from_md/release-notes/rl-2205.section.xml

@@ -132,6 +132,28 @@
           socket <literal>/run/redis-${serverName}/redis.sock</literal>.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          The option
+          <link linkend="opt-virtualisation.vmVariant">virtualisation.vmVariant</link>
+          was added to allow users to make changes to the
+          <literal>nixos-rebuild build-vm</literal> configuration that
+          do not apply to their normal system.
+        </para>
+        <para>
+          The <literal>config.system.build.vm</literal> attribute now
+          always exists and defaults to the value from
+          <literal>vmVariant</literal>. Configurations that import the
+          <literal>virtualisation/qemu-vm.nix</literal> module
+          themselves will override this value, such that
+          <literal>vmVariant</literal> is not used.
+        </para>
+        <para>
+          Similarly
+          <link linkend="opt-virtualisation.vmVariantWithBootLoader">virtualisation.vmVariantWithBootloader</link>
+          was added.
+        </para>
+      </listitem>
       <listitem>
         <para>
           The

nixos/doc/manual/release-notes/rl-2205.section.md

@@ -57,4 +57,14 @@ In addition to numerous new and upgraded packages, this release has the followin
   to the members of the Unix group `redis-${serverName}`
   through the Unix socket `/run/redis-${serverName}/redis.sock`.
 
+- The option [virtualisation.vmVariant](#opt-virtualisation.vmVariant) was added
+  to allow users to make changes to the `nixos-rebuild build-vm` configuration
+  that do not apply to their normal system.
+
+  The `config.system.build.vm` attribute now always exists and  defaults to the
+  value from `vmVariant`. Configurations that import the `virtualisation/qemu-vm.nix`
+  module themselves will override this value, such that `vmVariant` is not used.
+
+  Similarly [virtualisation.vmVariantWithBootloader](#opt-virtualisation.vmVariantWithBootLoader) was added.
+
 - The `writers.writePyPy2`/`writers.writePyPy3` and corresponding `writers.writePyPy2Bin`/`writers.writePyPy3Bin` convenience functions to create executable Python 2/3 scripts using the PyPy interpreter were added.