Travis-CI workers have cmake preinstalled, but Gitlab-CI Docker images
typically don't.
Signed-off-by: Simon McVittie <smcv@collabora.com>
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=108177 Acked-by: Philip Withnall <withnall@endlessm.com>
(cherry picked from commit 907832e00849ca454322052981dbb122ea537506)