ci/b2c: allow not specifying a reboot condition

This will allow us to only enable this feature where we need it.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Signed-off-by: Martin Roukala (né Peres) <martin.roukala@mupuf.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22596>

.gitlab-ci/b2c/b2c.yml.jinja2.jinja2

@@ -28,9 +28,11 @@ console_patterns:
     session_end:
         regex: >-
           {{ session_end_regex }}
+{% if session_reboot_regex %}
     session_reboot:
         regex: >-
           {{ session_reboot_regex }}
+{% endif %}
     job_success:
         regex: >-
           {{ job_success_regex }}