Unusual speedup observation

[Cvikli]

We had a discussion about a speedup when we built sysimage double times (replacing the older one).

Please see the discussion here: https://discourse.julialang.org/t/slow-julia-startup-time-after-sysimage-creation-and-an-unbelievable-observation/44102

It is a very big deal, because with this speed actually we can create many custom image and allow drastically faster development. If it found to be true with bigger names like this package organizer, then it should be noted in the julia's documentation for tips at workflow because this increase the adoption chance of the language with 10 fold, because it remove one of the main barrier for newbies.

[KristofferC]

Thanks for opening an issue about this. It is an interesting observation and we should figure out why it happens.