gitlab: reduce testing scope of check-gcov

gitlab: reduce testing scope of check-gcov

This keeps timing out on gitlab due to some qtests taking a long time.
As this is just ensuring the gcov machinery is working and not
attempting to be comprehensive lets skip qtest in this run.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230630180423.558337-4-alex.bennee@linaro.org>