support aborting on cache miss

[matthiasdiener]

What do you think @inducer? This would not only make debugging cache misses easier, it could also be used to automate determinism tests (by setting LOOPY_ABORT_ON_CACHE_MISS to something trueish, and rerunning the test).

[inducer]

I'm not wildly opposed, but I feel that it's also easy to just hack a 1/0 into that code path when needed. And for automated determinism tests, there are probably simpler approaches than to ask the codegen cache.

Also, "abort on cache miss" sounds like it would include all caches, but this applies to only one of many caches in loopy.