"Push only" mode for Build cache

[Marcin (Marcin Zajączkowski)]

@sterling

When we had problems with the Groovy compiler producing slightly different bytecode randomly for the same sources, we would see the hit rate jump around and had some hard to explain cache misses.

Btw, do you think having Groovy in production code can also cause different classpath order (somehow random, but with limited number of combinations) in dependent modules (which effectively reduces cache usefulness)?