This allows Gitlab to show a detailed test report in a human friendly
manner on a merge request page.
The junit output depends on Meson 0.55, but Meson in CI is bumped to the
latest release on Feb 15th. It is beneficial to use the newest
possible Meson in CI even if we do not require it, so that we benefit
from fixes, e.g. new warnings about accidentally using more recent
Meson features than our minimum Meson version supports.
Meson 0.57 is required for proper test names in the Gitlab report after
switching the tests to TAP. See:
https://github.com/mesonbuild/meson/issues/8316
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>