Force flush of stdout in new-testing for each line

In order to allow to watch live testing results, with tools like less +F.

If flush isn't forced, results are written in slurm output file only by blocks of many lines, not really practical to watch the progression of the tests.

@pswartva You need to enable the CI on your branch, such that I can accept your PR.

enabled an automatic merge when the pipeline for 3c65cbd5 succeeds

canceled the automatic merge

enabled an automatic merge when the pipeline for 3c65cbd5 succeeds

merged

mentioned in commit 08cf0cd1