Discussion: Allow multiple -Xjit args

[dsouzai]

Basically every component in OpenJ9 allows the user to specify the option prefex multiple times (for example the GC: -Xgc:verbose -Xgc:concurrentScavenge will result in both options getting applied). Additionally, having the ability to specify the option more than once without fear of the second overriding the first in its entirety is pretty standard behaviour; what we do is actually highly unintuitive and can cause all sorts of unintended behaviour.

I realize that there maybe some tests that depend on our existing behaviour, but the right way forward is to fix the tests. In terms of having this work in the compiler, it is actually incredibly easy - we just read all the -Xjit strings and concatenate into one big string before passing it over to the bulk of the options processing; probably <20 lines of code.