Use (implicitly) parallel tests on new enough automake. The tests run
a bit quicker with this change. On my laptop, I measured 27 mins down
to 18 mins.
Change the ./run function so that ./run --test no longer spools the
test output to a file. That is not necessary when using parallel
tests, since the test harness does the same thing.
Note: This commit removes the $RUN_OUTPUT_FILE functionality. We will
change the CI integration in a future commit so it uses the .trs and
.log files.
c0a781ed9a