Better setup for running partest in the CI.
Better setup for running partest in the CI.

* Make sure that we take our SBT_OPTS into account, using a new
  function `sbtnoretry` (which we also use in some other places).
* Add a re-display of the failed command when there is no more
  retry.
* Compile all the dependencies of `partestSuite/testOnly` in a
  first run of `sbtnoretry`, to have less in memory by the time
  we actually start partest.

sjrd/scala-js,scala-js/scala-js,sjrd/scala-js,scala-js/scala-js,scala-js/scala-js,sjrd/scala-js