ci: Run tests on i386 cross builds

Yes, some tests fail, but we can turn those into XFAILs at meson time.
Better to keep the things that work working than not cover them at all.
Unfortunately XPASS results will not cause the build to fail until we
update CI to meson 0.51 or newer.

Reviewed-by: Daniel Stone <daniels@collabora.com>
38 jobs for !2002 with ci-i386-tests in 15 minutes and 56 seconds (queued for 5 seconds)
merge request