windows GC crash
* see reproducing example here: https://github.com/genotrance/nimterop/pull/83
* from @genotrance :
  * Araq suggested --gc:markAndSweep
  * but still no clue why it crashes and minimal example is going to be hard to come by
  * ~~does that mean user code has to use it when importing nimterop? that wouldn't be good~~ EDIT : toast only

