When a runner becomes idle, split remaining jobs and let it run that

[joakimk]

I've tried to optimize by balancing the cpu load but that hasn't been very successful. What could be successful is using all the cpu of the cluster by running incomplete jobs in smaller and smaller parts until all files are done at which point the entire build is removed and any unneeded jobs are stopped (given that #6 is done).

[joakimk]

If the chunks are still too big, there is the option of running parts of files (I've got some code for this with cucumber scenarios in a branch).

[joakimk]

I've done some trials on this. It does work, but there is no huge win and it is worse at balancing between builds.