Documentation: kunit: Cleanup run_wrapper, fix x-ref

The "Run Tests on qemu" section of run_wrapper.rst had a few issues left
over from the last big documentation refactor[1]:
- It referenced a non_uml.rst page, which was integrated into the other
  pages (including run_wrapper.rst).
- It skimmed over the use of --arch= and --cross_compile= in favour of
  using a custom --qemu_config. Since most users will want to use the
  former, let's give examples.

Remove the reference to the non-existant page, and add a couple of
examples to encourage the use of --arch= and --cross_compile=.

With this change, there should be no more broken references in the KUnit
documentation (i.e., the one mentioned in [2] is gone).

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=46201d47d6c4be594c1d57b7f3251c371626a9c4
[2]: https://lore.kernel.org/linux-doc/cover.1656234456.git.mchehab@kernel.org/Signed-off-by: David Gow <davidgow@google.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Documentation/dev-tools/kunit/run_wrapper.rst

@@ -192,6 +192,21 @@ via UML. To run tests on qemu, by default it requires two flags:
     if we have downloaded the microblaze toolchain from the 0-day
     website to a directory in our home directory called toolchains.
 
+This means that for most architectures, running under qemu is as simple as:
+
+.. code-block:: bash
+
+	./tools/testing/kunit/kunit.py run --arch=x86_64
+
+When cross-compiling, we'll likely need to specify a different toolchain, for
+example:
+
+.. code-block:: bash
+
+	./tools/testing/kunit/kunit.py run \
+		--arch=s390 \
+		--cross_compile=s390x-linux-gnu-
+
 If we want to run KUnit tests on an architecture not supported by
 the ``--arch`` flag, or want to run KUnit tests on qemu using a
 non-default configuration; then we can write our own``QemuConfig``.
@@ -214,9 +229,6 @@ as
 		--jobs=12 \
 		--qemu_config=./tools/testing/kunit/qemu_configs/x86_64.py
 
-To run existing KUnit tests on non-UML architectures, see:
-Documentation/dev-tools/kunit/non_uml.rst.
-
 Command-Line Arguments
 ======================