Issue Description:

There are times when you need to alter package compilation differently for simulator vs device builds. For example, not all system frameworks are available in the simulator that are present on device. In these cases you need conditional linking flags. Or alternatively, you have a library that needs to be linked in, but ONLY on simulator builds.

Right now I can only specify BuildSettingConditions based on the platform or the BuildConfiguration, neither of which will detect when I'm building for simulator.