Choose the Garbage Collector used by the translated program.
The good performing collectors are "hybrid" and "minimark".
The default is "minimark".

  - "ref": reference counting. Takes very long to translate and the result is
    slow.

  - "marksweep": naive mark & sweep.

  - "semispace": a copying semi-space GC.

  - "generation": a generational GC using the semi-space GC for the
    older generation.

  - "boehm": use the Boehm conservative GC.

  - "hybrid": a hybrid collector of "generation" together with a
    mark-n-sweep old space

  - "markcompact": a slow, but memory-efficient collector,
    influenced e.g. by Smalltalk systems.

  - "minimark": a generational mark-n-sweep collector with good
    performance.  Includes page marking for large arrays.
