One of the main reasons to have custom runners it so we can run KVM
tests. Enable the "kvm" additional group so we can access the feature
on the kernel.

Message-Id: <20230503091244.1450613-5-alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reported-by: Peter Maydell <peter.maydell@linaro.org>