mariadb includes libevent.dylib in archcheck.files but declares no dependency on the libevent port. Either libevent should be added to the dependencies, or the check for libevent.dylib should be removed from archcheck.files. My installed mariadb does not link with libevent, though I do see occurrences of libevent in the sources. Maybe it's an optional dependency.
While we're looking at dependencies, I'm curious why mariadb lists a library dependency on cmake. Does it really use cmake at runtime? If so, a comment should be added to the port explaining this, since it's unusual. If not, then the cmake portgroup's build dependency on cmake should be sufficient.