The meson_args variable was added in commit 3b4da132, but
was not used in that commit and isn't used today.  Delete the
unnecessary assignment.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20220825150703.4074125-3-peter.maydell@linaro.org