Use cache=True on everything?

[NicolasHug]

Opened numba/numba#3588 to ask if there's an alternative.

[NicolasHug]

There's none (for now).

Do we want to cache all compilations @ogrisel ? I'd say yes, since it takes a non-negligible amount of time

[NicolasHug]

So I did that, cache=True is not supported for jitclasses nor when parallel=True so gain is pretty minimal: going from about 10s to 9s.

[ogrisel]

Ok so better wait for a better caching infrastructure in numba before enabling it.