I use MacPorts to install and update two versions of ruby (1.8.7 and 1.9.2). How to make gems of both versions be in sync? Is it possible to use same directory for gems, but make native extensions to be built in separate places? Please don't direct me to rvm.
I don't think this is feasible. It might be possible with some kind of complex hack, but it would be a nightmare to maintain especially if they're sharing the same directory.
Is there a specific reason you want to avoid RVM? Using RVM is the only way I know to manage multiple rubies on the same machine and still sleep well at night.