This allows to set a job tag dynamically.
We need this to be able to select the Kubernetes runner.
See https://wiki.qemu.org/Testing/CI/KubernetesRunners

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Signed-off-by: Camilla Conte <cconte@redhat.com>
Message-Id: <20230522174153.46801-5-cconte@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>