That's currently not possible to do, except for triggering builds in silent mode.
The problem with _not_ joining the results is that each build would then override the review vote of the previous one.
So one quick build could vote say Verified +1 allowing the patch to be merged, and maybe is, but 15 min later one test fails and wants to put -1 but can't since the change is merged already.
Or two quick builds fails voting -1 and 15 min later another job's build succeeds and overwrites the result with +1 allowing it to be merged even though it shouldn't be.
There are plans for a "job grouping" feature where the idea is that you could group for example fast jobs together in one group and slow jobs in another and so on. and the trigger would send intermediate results for each group (you could potentially have each job in its own group here) But only negative results would actually get votes, positive results would not get its vote until every build is done, but you would at least get quick turnaround for failing builds.
/B