main's argument vector can't be logged or compared properly #2639

Since I changed shape glue to treat vectors as boxes containing an unboxed vector, glue operations don't work on the vector main is given. This is because the runtime doesn't now how to construct a type descriptor to put in the box, so the shape glue gives up. This would also happen for other arrays returned by the runtime, like the environment.

The ideal solution might be to not ever need to build rust vectors from the C++ runtime code, but the straightforward solution is for the runtime to have hardcoded type descriptors for the vectors it creates.